Regulation of Hmg-Coa Reductase Degradation Requires the P-Type Atpase Cod1p/Spf1p

The integral ER membrane protein HMG-CoA reductase (HMGR) is a key enzyme of the mevalonate pathway from which sterols and other essential molecules are produced. HMGR degradation occurs in the ER and is regulated by mevalonate-derived signals. Little is known about the mechanisms responsible for regulating HMGR degradation. The yeast Hmg2p isozyme of HMGR undergoes regulated degradation in a manner very similar to mammalian HMGR, allowing us to isolate mutants deficient in regulating Hmg2p stability. We call these mutants cod mutants for the control of HMG-CoA reductase degradation. With this screen, we have identified the first gene of this class, COD1, which encodes a P-type ATPase and is identical to SPF1. Our data suggested that Cod1p is a calcium transporter required for regulating Hmg2p degradation. This role for Cod1p is distinctly different from that of the well-characterized Ca2+ P-type ATPase Pmr1p which is neither required for Hmg2p degradation nor its control. The identification of Cod1p is especially intriguing in light of the role Ca2+ plays in the regulated degradation of mammalian HMGR.

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Regulated degradation of HMG-CoA reductase, an integral membrane protein of the endoplasmic reticulum, in yeast.

The Journal of Cell Biology ◽

10.1083/jcb.125.2.299 ◽

1994 ◽

Vol 125 (2) ◽

pp. 299-312 ◽

Cited By ~ 139

Author(s):

R Y Hampton ◽

J Rine

Keyword(s):

Mevalonate Pathway ◽

Integral Membrane Protein ◽

Integral Membrane Proteins ◽

Hmg Coa Reductase ◽

Key Enzyme ◽

Farnesylated Protein ◽

The Stability ◽

Coa Reductase ◽

Pathway Flux

Numerous integral membrane proteins are degraded in the mammalian ER. HMG-CoA reductase (HMG-R), a key enzyme in the mevalonate pathway by which isoprenoids and sterols are synthesized, is one substrate of ER degradation. The degradation of HMG-R is modulated by feedback signals from the mevalonate pathway. We investigated the role of regulated degradation of the two isozymes of HMG-R, Hmg1p and Hmg2p, in the physiology of Saccharomyces cerevisiae. Hmg1p was quite stable, whereas Hmg2p was rapidly degraded. Degradation of Hmg2p proceeded independently of vacuolar proteases or secretory traffic, indicating that Hmg2p degradation occurred at the ER. Hmg2p stability was strongly affected by modulation of the mevalonate pathway through pharmacological or genetic means. Decreased mevalonate pathway flux resulted in decreased degradation of Hmg2p. One signal for degradation of Hmg2p was a nonsterol, mevalonate-derived molecule produced before the synthesis of squalene. Genetic evidence indicated that a farnesylated protein may also be necessary for Hmg2p degradation. Studies with reporter genes demonstrated that the stability of each isozyme was determined by its noncatalytic NH2-terminal domain. Our data show that ER protein degradation is widely conserved among eukaryotes, and that feedback control of HMG-R degradation is an ancient paradigm of regulation.

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Inhibition of protein geranylgeranylation induces apoptosis in myeloma plasma cells by reducing Mcl-1 protein levels

Blood ◽

10.1182/blood-2003-03-0970 ◽

2003 ◽

Vol 102 (9) ◽

pp. 3354-3362 ◽

Cited By ~ 85

Author(s):

Niels W. C. J. van de Donk ◽

Marloes M. J. Kamphuis ◽

Berris van Kessel ◽

Henk M. Lokhorst ◽

Andries C. Bloem

Keyword(s):

Multiple Myeloma ◽

Plasma Cells ◽

Mevalonate Pathway ◽

Cytochrome C Release ◽

Hmg Coa Reductase ◽

Myeloma Cells ◽

Protein Levels ◽

Geranylgeranyl Transferase ◽

Induced Apoptosis ◽

Coa Reductase

AbstractHMG-CoA reductase is the rate-limiting enzyme of the mevalonate pathway leading to the formation of cholesterol and isoprenoids such as farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP). The inhibition of HMG-CoA reductase by lovastatin induced apoptosis in plasma cell lines and tumor cells from patients with multiple myeloma. Here we show that cotreatment with mevalonate or geranylgeranyl moieties, but not farnesyl groups, rescued myeloma cells from lovastatin-induced apoptosis. In addition, the inhibition of geranylgeranylation by specific inhibition of geranylgeranyl transferase I (GGTase I) induced the apoptosis of myeloma cells. Apoptosis triggered by the inhibition of geranylgeranylation was associated with reduction of Mcl-1 protein expression, collapse of the mitochondrial transmembrane potential, expression of the mitochondrial membrane protein 7A6, cytochrome c release from mitochondria into the cytosol, and stimulation of caspase-3 activity. These results imply that protein geranylgeranylation is critical for regulating myeloma tumor cell survival, possibly through regulating Mcl-1 expression. Our results show that pharmacologic agents such as lovastatin or GGTase inhibitors may be useful in the treatment of multiple myeloma.

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Lovastatin as Salvage Immunomodulatory Therapy in Patients with Refractory and Relapsed Multipla Myeloma.

Blood ◽

10.1182/blood.v106.11.1567.1567 ◽

2005 ◽

Vol 106 (11) ◽

pp. 1567-1567 ◽

Cited By ~ 1

Author(s):

Marek Hus ◽

Norbert Grzasko ◽

Dariusz Jawniak ◽

Marta Szostek ◽

Anna Dmoszynska

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Light Chain ◽

Protein Level ◽

Mevalonate Pathway ◽

Sinus Bradycardia ◽

Autologous Transplantation ◽

M Protein ◽

Hmg Coa Reductase ◽

Coa Reductase

Abstract In the recent years the treatment of patients with multiple myeloma (MM) has changed because of the introduction of new agents, mainly thalidomide (THAL) and its derivatives and bortezomib, an inhibitor of the 20S proteasome. Lovastatin (LOV) and other inhibitors of HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway, have been demonstrated to exibit antineoplasmatic and proapoptotic properties in numerous in vitro studies involving myeloma cell lines including our own experiments. This observation induced us to administer LOV in combination with THAL and dexamethasone (DEX). We report here our preliminary experiences with THAL and LOV therapy in patients with refractory and relapsed MM. We have treated 81 patients with THAL+DEX regimen (TD) or THAL+DEX+LOV regimen (TLD). Patients received drugs orally in 28 day cycles. THAL was given from day 1 to day 28 each cycle and it was started at a initial dose of 100 mg daily increased to 300 mg daily. DEX was administered at a dose of 40 mg daily in days 1–4 each cycle. LOV was administered at a dose of 2 mg/kg in days 1–5 and 8–12 and at a dose of 0.5 mg/kg in days 15–28 each cycle. TLD regimen was administered to 43 patients and TD regimen to 38 patients. Patients characteristics before treatment were as follows: the median age 61.2 years; 61% of patients IgG, 26% IgA, 7% light chain and 6% other; 76% of patients were light chain kappa and 24% lambda; median serum M-protein level was 4.2 g/dl, bone marrow plasma cells 47%, hemoglobin 10.1 g/dl, platelets 197 G/l, beta-2-microglobulin 4.2 mg/ml, albumin 3.9 g/dl and LDH 292 IU. The median follow-up was 29 month. A clinical response, defined as a reduction of M-protein level by 50% or more, was observed in 67.8% of patients in TD group and in 88.0% in TLD group. CR i NCR was observed in 35.0% and 62.7% respectively. In 11 TLD (25.5%.) and 4 TD (10.5%) patients successful stem cell harvest was performed and mean amount of collected CD34+ cells was 8.2*106/kg. Successful autologous transplantation was performed in 8 patients from this group. Overall survival in TLD group (median 23.0 months) was significantly longer than in TD group (median 18.0 months). Similarly event free survival was longer in TLD (median 7.0 months) group than in TD group (4.5 months). We observed significant negative correlation between response and bone marrow infiltration (p=0.008), M-protein level (p=0.0004) and positive correlation between response and albumin level (p=0.005). Short time to reduction of M-protein by 50% was connected with better response. Common side effects as somnolence, fatigue and constipation were observed in about 45% of patients in TLD and TD groups. In 2 TLD and in 3 TD patients we diagnosed deep vein thrombosis. In 2 TLD patients sinus bradycardia was observed. Our results suggest that addition of LOV to THAL and DEX improves response rate in patients with refactory and relapsed MM. Moreover it is possible to harvest stem cells and perform autologous stem cells graft in patients treated with such regimen. A future prospective randomised study is needed to confirm the value of LOV or other HMG-CoA reductase inhibitors in the treatment of MM patients.

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Modulation of YAP/ TAZ by statins to improve survival in epithelioid hemangioendothelioma (EHE).

Journal of Clinical Oncology ◽

10.1200/jco.2020.38.15_suppl.e23527 ◽

2020 ◽

Vol 38 (15_suppl) ◽

pp. e23527-e23527

Author(s):

Aparna Subramaniam ◽

Jing Zheng ◽

Sudha Yalamanchili ◽

Anthony Paul Conley ◽

Ravin Ratan ◽

...

Keyword(s):

Mevalonate Pathway ◽

Hippo Pathway ◽

Nuclear Accumulation ◽

Rank Test ◽

Cancer Center ◽

Hmg Coa Reductase ◽

Number Of Patients ◽

The Mean ◽

Coa Reductase ◽

Statin Use

e23527 Background: EHE is a rare soft tissue tumor of endothelial origin. It is distinguished by the pathognomonic WWTR1-CAMTA1 fusion (WWTR1 is the gene symbol for TAZ) seen in 90% of the tumors. YAP1-TFE3 fusion is less common and seen in 10% of the tumors. YAP and TAZ are critical downstream effectors of the Hippo pathway that regulate tumor development, progression, invasion and metastasis by modulating the expression of many Hippo pathway targets. Recent studies have shown that inhibition of HMG-CoA reductase, a key enzyme of the mevalonate pathway, can regulate YAP/ TAZ by preventing their nuclear accumulation and inhibiting their transcriptional activity. This has led to interest in the role of statins, which inhibit HMG-CoA reductase, as a modulator of YAP/ TAZ that could benefit patients with sarcoma, particularly EHE. Methods: A retrospective analysis was performed on patients with a diagnosis of EHE at M D Anderson Cancer Center. Patients were identified using the electronic database system and screened for statin use using EMRs. Demographic and clinical characteristics were tabulated. KM method was used to assess overall survival and log rank test was used to test survival differences between the statin use and non- statin use groups. All statistical analysis was performed using STATA 14. Results: 226 patients with EHE were identified. 27 of them had recorded statin use during the course of their disease. The median OS for the statin use group was not reached and the mean OS was 221 months. The median OS for the non- statin use group was 123.9 months, while the mean OS was 160 months. The difference in OS was not statistically significant between the two groups. The median follow-up time for our cohort was 36.6 months. Conclusions: Our findings indicate a trend towards improved survival for patients with EHE who have received statins over the course of their disease. Our study is limited by a small number of patients who received statins. Prospective studies are required to assess the therapeutic benefit of statins in EHE. [Table: see text]

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Identification, Evolution, and Essentiality of the Mevalonate Pathway for Isopentenyl Diphosphate Biosynthesis in Gram-Positive Cocci

Journal of Bacteriology ◽

10.1128/jb.182.15.4319-4327.2000 ◽

2000 ◽

Vol 182 (15) ◽

pp. 4319-4327 ◽

Cited By ~ 163

Author(s):

E. Imogen Wilding ◽

James R. Brown ◽

Alexander P. Bryant ◽

Alison F. Chalker ◽

David J. Holmes ◽

...

Keyword(s):

Mevalonate Pathway ◽

Genomic Analysis ◽

Eukaryotic Cell ◽

Infection Model ◽

Isopentenyl Diphosphate ◽

Gram Positive ◽

Hmg Coa Reductase ◽

Coa Reductase ◽

Gram Positive Cocci

ABSTRACT The mevalonate pathway and the glyceraldehyde 3-phosphate (GAP)–pyruvate pathway are alternative routes for the biosynthesis of the central isoprenoid precursor, isopentenyl diphosphate. Genomic analysis revealed that the staphylococci, streptococci, and enterococci possess genes predicted to encode all of the enzymes of the mevalonate pathway and not the GAP-pyruvate pathway, unlike Bacillus subtilis and most gram-negative bacteria studied, which possess only components of the latter pathway. Phylogenetic and comparative genome analyses suggest that the genes for mevalonate biosynthesis in gram-positive cocci, which are highly divergent from those of mammals, were horizontally transferred from a primitive eukaryotic cell. Enterococci uniquely encode a bifunctional protein predicted to possess both 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and acetyl-CoA acetyltransferase activities. Genetic disruption experiments have shown that five genes encoding proteins involved in this pathway (HMG-CoA synthase, HMG-CoA reductase, mevalonate kinase, phosphomevalonate kinase, and mevalonate diphosphate decarboxylase) are essential for the in vitro growth of Streptococcus pneumoniae under standard conditions. Allelic replacement of the HMG-CoA synthase gene rendered the organism auxotrophic for mevalonate and severely attenuated in a murine respiratory tract infection model. The mevalonate pathway thus represents a potential antibacterial target in the low-G+C gram-positive cocci.

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Identification of the sequences in HMG-CoA reductase required for karmellae assembly.

Molecular Biology of the Cell ◽

10.1091/mbc.6.11.1535 ◽

1995 ◽

Vol 6 (11) ◽

pp. 1535-1547 ◽

Cited By ~ 37

Author(s):

M L Parrish ◽

C Sengstag ◽

J D Rine ◽

R L Wright

Keyword(s):

Cellular Responses ◽

Cell Periphery ◽

Membrane Domain ◽

Hmg Coa Reductase ◽

Simple Possibility ◽

Coa Reductase ◽

Necessary And Sufficient ◽

Specific Membrane ◽

Molecular Nature ◽

Er Membrane

In all eukaryotic cells that have been examined, specific membrane arrays are induced in response to increased levels of the ER membrane protein, HMG-CoA reductase. Analysis of these inducible membranes has the potential to reveal basic insights into general membrane assembly. Yeast express two HMG-CoA reductase isozymes, and each isozyme induces a morphologically distinct proliferation of the endoplasmic reticulum. The isozyme encoded by HMG1 induces karmellae, which are long stacks of membranes that partially enclose the nucleus. In contrast, the isozyme encoded by HMG2 induces short stacks of membrane that may be associated with the nucleus, but are frequently present at the cell periphery. To understand the molecular nature of the different cellular responses to Hmg1p and Hmg2p, we mapped the region of Hmg1p that is needed for karmellae assembly. For this analysis, a series of exchange alleles was examined in which a portion of the Hmg2p membrane domain was replaced with the corresponding Hmg1p sequences. Results of this analysis indicated that the ER lumenal loop between predicted transmembrane domains 6 and 7 was both necessary and sufficient for karmellae assembly, when present in the context of an HMG-CoA reductase membrane domain. Immunoblotting experiments ruled out the simple possibility that differences in the amounts of the various chimeric HMG-CoA reductase proteins was responsible for the altered cellular responses. Our results are consistent with the hypothesis that each yeast isozyme induces or organizes a qualitatively different organization of ER membrane.

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Different subcellular localization of Saccharomyces cerevisiae HMG-CoA reductase isozymes at elevated levels corresponds to distinct endoplasmic reticulum membrane proliferations.

Molecular Biology of the Cell ◽

10.1091/mbc.7.5.769 ◽

1996 ◽

Vol 7 (5) ◽

pp. 769-789 ◽

Cited By ~ 81

Author(s):

A J Koning ◽

C J Roberts ◽

R L Wright

Keyword(s):

Saccharomyces Cerevisiae ◽

Endoplasmic Reticulum ◽

Subcellular Localization ◽

Nuclear Envelope ◽

Fluorescent Protein ◽

Endoplasmic Reticulum Membrane ◽

Hmg Coa Reductase ◽

Endogenous Expression ◽

Coa Reductase ◽

Er Membrane

In all eucaryotic cell types analyzed, proliferations of the endoplasmic reticulum (ER) can be induced by increasing the levels of certain integral ER proteins. One of the best characterized of these proteins is HMG-CoA reductase, which catalyzes the rate-limiting step in sterol biosynthesis. We have investigated the subcellular distributions of the two HMG-CoA reductase isozymes in Saccharomyces cerevisiae and the types of ER proliferations that arise in response to elevated levels of each isozyme. At endogenous expression levels, Hmg1p and Hmg2p were both primarily localized in the nuclear envelope. However, at increased levels, the isozymes displayed distinct subcellular localization patterns in which each isozyme was predominantly localized in a different region of the ER. Specifically, increased levels of Hmg1p were concentrated in the nuclear envelope, whereas increased levels of Hmg2p were concentrated in the peripheral ER. In addition, an Hmg2p chimeric protein containing a 77-amino acid lumenal segment from Hmg1p was localized in a pattern that resembled that of Hmg1p when expressed at increased levels. Reflecting their different subcellular distributions, elevated levels of Hmg1p and Hmg2p induced sets of ER membrane proliferations with distinct morphologies. The ER membrane protein, Sec61p, was localized in the membranes induced by both Hmg1p and Hmg2p green fluorescent protein (GFP) fusions. In contrast, the lumenal ER protein, Kar2p, was present in Hmg1p:GFP membranes, but only rarely in Hmg2p:GFP membranes. These results indicated that the membranes synthesized in response to Hmg1p and Hmg2p were derived from the ER, but that the membranes were not identical in protein composition. We determined that the different types of ER proliferations were not simply due to quantitative differences in protein amounts or to the different half-lives of the two isozymes. It is possible that the specific distributions of the two yeast HMG-CoA reductase isozymes and their corresponding membrane proliferations may reveal regions of the ER that are specialized for certain branches of the sterol biosynthetic pathway.

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Purification, Characterization, and Cloning of a Eubacterial 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase, a Key Enzyme Involved in Biosynthesis of Terpenoids

Journal of Bacteriology ◽

10.1128/jb.181.4.1256-1263.1999 ◽

1999 ◽

Vol 181 (4) ◽

pp. 1256-1263 ◽

Cited By ~ 42

Author(s):

Shunji Takahashi ◽

Tomohisa Kuzuyama ◽

Haruo Seto

Keyword(s):

Amino Acid ◽

Coenzyme A ◽

Polyacrylamide Gel Electrophoresis ◽

Sodium Dodecyl ◽

Gel Filtration ◽

Ph Optimum ◽

Hmg Coa Reductase ◽

Apparent Homogeneity ◽

Key Enzyme ◽

Coa Reductase

ABSTRACT The eubacterial 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (EC 1.1.1.34 ) was purified 3,000-fold fromStreptomyces sp. strain CL190 to apparent homogeneity with an overall yield of 2.1%. The purification procedure consisted of (NH4)2SO4 precipitation, heat treatment and anion exchange, hydrophobic interaction, and affinity chromatographies. The molecular mass of the enzyme was estimated to be 41 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 100 to 105 kDa by gel filtration chromatography, suggesting that the enzyme is most likely to be a dimer. The enzyme showed a pH optimum of around 7.2, with apparent Km values of 62 μM for NADPH and 7.7 μM for HMG-CoA. A gene from CL190 responsible for HMG-CoA reductase was cloned by the colony hybridization method with an oligonucleotide probe synthesized on the basis of the N-terminal sequence of the purified enzyme. The amino acid sequence of the CL190 HMG-CoA reductase revealed several limited motifs which were highly conserved and common to the eucaryotic and archaebacterial enzymes. These sequence conservations suggest a strong evolutionary pressure to maintain amino acid residues at specific positions, indicating that the conserved motifs might play important roles in the structural conformation and/or catalytic properties of the enzyme.

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Depletion of essential isoprenoids and ER stress induction following acute liver-specific deletion of HMG-CoA reductase

The Journal of Lipid Research ◽

10.1194/jlr.ra120001006 ◽

2020 ◽

Vol 61 (12) ◽

pp. 1675-1686

Author(s):

Marco De Giorgi ◽

Kelsey E. Jarrett ◽

Jason C. Burton ◽

Alexandria M. Doerfler ◽

Ayrea Hurley ◽

...

Keyword(s):

Er Stress ◽

Mevalonate Pathway ◽

Critical Role ◽

Cellular Level ◽

Hmg Coa Reductase ◽

Biochemical Level ◽

Genetic Deletion ◽

Coa Reductase ◽

Rate Limiting ◽

Specific Deletion

HMG-CoA reductase (Hmgcr) is the rate-limiting enzyme in the mevalonate pathway and is inhibited by statins. In addition to cholesterol, Hmgcr activity is also required for synthesizing nonsterol isoprenoids, such as dolichol, ubiquinone, and farnesylated and geranylgeranylated proteins. Here, we investigated the effects of Hmgcr inhibition on nonsterol isoprenoids in the liver. We have generated new genetic models to acutely delete genes in the mevalonate pathway in the liver using AAV-mediated delivery of Cre-recombinase (AAV-Cre) or CRISPR/Cas9 (AAV-CRISPR). The genetic deletion of Hmgcr by AAV-Cre resulted in extensive hepatocyte apoptosis and compensatory liver regeneration. At the biochemical level, we observed decreased levels of sterols and depletion of the nonsterol isoprenoids, dolichol and ubiquinone. At the cellular level, Hmgcr-null hepatocytes showed ER stress and impaired N-glycosylation. We further hypothesized that the depletion of dolichol, essential for N-glycosylation, could be responsible for ER stress. Using AAV-CRISPR, we somatically disrupted dehydrodolichyl diphosphate synthase subunit (Dhdds), encoding a branch point enzyme required for dolichol biosynthesis. Dhdds-null livers showed ER stress and impaired N-glycosylation, along with apoptosis and regeneration. Finally, the combined deletion of Hmgcr and Dhdds synergistically exacerbated hepatocyte ER stress. Our data show a critical role for mevalonate-derived dolichol in the liver and suggest that dolichol depletion is at least partially responsible for ER stress and apoptosis upon potent Hmgcr inhibition.

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Enterococcus faecalis Acetoacetyl-Coenzyme A Thiolase/3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase, a Dual-Function Protein of Isopentenyl Diphosphate Biosynthesis

Journal of Bacteriology ◽

10.1128/jb.184.8.2116-2122.2002 ◽

2002 ◽

Vol 184 (8) ◽

pp. 2116-2122 ◽

Cited By ~ 45

Author(s):

Matija Hedl ◽

Autumn Sutherlin ◽

E. Imogen Wilding ◽

Marie Mazzulla ◽

Damien McDevitt ◽

...

Keyword(s):

Gene Product ◽

Enterococcus Faecalis ◽

Active Site ◽

Coenzyme A ◽

Mevalonate Pathway ◽

Dual Function ◽

Isopentenyl Diphosphate ◽

Hmg Coa Reductase ◽

Coa Reductase ◽

Active Site Histidine

ABSTRACT Many bacteria employ the nonmevalonate pathway for synthesis of isopentenyl diphosphate, the monomer unit for isoprenoid biosynthesis. However, gram-positive cocci exclusively use the mevalonate pathway, which is essential for their growth (E. I. Wilding et al., J. Bacteriol. 182:4319-4327, 2000). Enzymes of the mevalonate pathway are thus potential targets for drug intervention. Uniquely, the enterococci possess a single open reading frame, mvaE, that appears to encode two enzymes of the mevalonate pathway, acetoacetyl-coenzyme A thiolase and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Western blotting revealed that the mvaE gene product is a single polypeptide in Enterococcus faecalis, Enterococcus faecium, and Enterococcus hirae. The mvaE gene was cloned from E. faecalis and was expressed with an N-terminal His tag in Escherichia coli. The gene product was then purified by nickel affinity chromatography. As predicted, the 86.5-kDa mvaE gene product catalyzed both the acetoacetyl-CoA thiolase and HMG-CoA reductase reactions. Temperature optima, ΔHa and Km values, and pH optima were determined for both activities. Kinetic studies of acetoacetyl-CoA thiolase implicated a ping-pong mechanism. CoA acted as an inhibitor competitive with acetyl-CoA. A millimolar Ki for a statin drug confirmed that E. faecalis HMG-CoA reductase is a class II enzyme. The oxidoreductant was NADP(H). A role for an active-site histidine during the first redox step of the HMG-CoA, reductase reaction was suggested by the ability of diethylpyrocarbonate to block formation of mevalonate from HMG-CoA, but not from mevaldehyde. Sequence comparisons with other HMG-CoA reductases suggest that the essential active-site histidine is His756. The mvaE gene product represents the first example of an HMG-CoA reductase fused to another enzyme.

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