Employing Calorimetric Methods to Determine the Mechanism of the Invertase Maximal Activity Delay

Parra et al. ( Acta Physiol. Scand 169: 157–165, 2000) showed that 2 wk of daily sprint interval training (SIT) increased citrate synthase (CS) maximal activity but did not change “anaerobic” work capacity, possibly because of chronic fatigue induced by daily training. The effect of fewer SIT sessions on muscle oxidative potential is unknown, and aside from changes in peak oxygen uptake (V̇o2 peak), no study has examined the effect of SIT on “aerobic” exercise capacity. We tested the hypothesis that six sessions of SIT, performed over 2 wk with 1–2 days rest between sessions to promote recovery, would increase CS maximal activity and endurance capacity during cycling at ∼80% V̇o2 peak. Eight recreationally active subjects [age = 22 ± 1 yr; V̇o2 peak = 45 ± 3 ml·kg−1·min−1 (mean ± SE)] were studied before and 3 days after SIT. Each training session consisted of four to seven “all-out” 30-s Wingate tests with 4 min of recovery. After SIT, CS maximal activity increased by 38% (5.5 ± 1.0 vs. 4.0 ± 0.7 mmol·kg protein−1·h−1) and resting muscle glycogen content increased by 26% (614 ± 39 vs. 489 ± 57 mmol/kg dry wt) (both P < 0.05). Most strikingly, cycle endurance capacity increased by 100% after SIT (51 ± 11 vs. 26 ± 5 min; P < 0.05), despite no change in V̇o2 peak. The coefficient of variation for the cycle test was 12.0%, and a control group ( n = 8) showed no change in performance when tested ∼2 wk apart without SIT. We conclude that short sprint interval training (∼15 min of intense exercise over 2 wk) increased muscle oxidative potential and doubled endurance capacity during intense aerobic cycling in recreationally active individuals.

Download Full-text

Characterization of a Solvent-Tolerant Amidohydrolase Involved in Natural Product Heterocycle Formation

Catalysts ◽

10.3390/catal11080892 ◽

2021 ◽

Vol 11 (8) ◽

pp. 892

Author(s):

Lea Winand ◽

Dustin Joshua Vollmann ◽

Jacqueline Hentschel ◽

Markus Nett

Keyword(s):

Natural Product ◽

Metal Ion ◽

Building Blocks ◽

Maximal Activity ◽

Kinetic Properties ◽

Pharmaceutical Drugs ◽

Highly Active ◽

Km Value ◽

Amidohydrolase Superfamily ◽

Solvent Tolerant

Heterocycles are important building blocks in pharmaceutical drugs and their enzymatic synthesis is attracting increasing interest. In recent years, various enzymes of the amidohydrolase superfamily were reported to catalyze heterocycle-forming condensation reactions. One of these enzymes, MxcM, is biochemically and kinetically characterized in this study. MxcM generates an imidazoline moiety in the biosynthesis of the natural product pseudochelin A, which features potent anti-inflammatory properties. The enzyme shows maximal activity at 50 °C and pH 10 as well as a kcat/Km value of 22,932 s−1 M−1 at its temperature optimum. Experimental data suggest that the activity of MxcM does not depend on a catalytic metal ion, which is uncommon among amidohydrolases. MxcM is highly active in diverse organic solvents and concentrated salt solutions. Furthermore, we show that MxcM is also capable to introduce imidazoline rings into derivatives of its natural substrate myxochelin B. Overall, MxcM is a solvent-stable, halotolerant enzyme with promising biochemical and kinetic properties and, in future, might become a valuable biocatalyst for the manufacturing of pharmaceutical drugs.

Download Full-text

Exploring the taxonomical and functional profile of As Burgas hot spring focusing on thermostable β-galactosidases

Scientific Reports ◽

10.1038/s41598-020-80489-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

María-Eugenia DeCastro ◽

Michael P. Doane ◽

Elizabeth Ann Dinsdale ◽

Esther Rodríguez-Belmonte ◽

María-Isabel González-Siso

Keyword(s):

Microbial Community ◽

Hot Spring ◽

Functional Characterization ◽

Tca Cycle ◽

Maximal Activity ◽

Sulfur Cycle ◽

E Coli ◽

Complex Microbial Community ◽

Relationship Of ◽

The Relationship

AbstractIn the present study we investigate the microbial community inhabiting As Burgas geothermal spring, located in Ourense (Galicia, Spain). The approximately 23 Gbp of Illumina sequences generated for each replicate revealed a complex microbial community dominated by Bacteria in which Proteobacteria and Aquificae were the two prevalent phyla. An association between the two most prevalent genera, Thermus and Hydrogenobacter, was suggested by the relationship of their metabolism. The high relative abundance of sequences involved in the Calvin–Benson cycle and the reductive TCA cycle unveils the dominance of an autotrophic population. Important pathways from the nitrogen and sulfur cycle are potentially taking place in As Burgas hot spring. In the assembled reads, two complete ORFs matching GH2 beta-galactosidases were found. To assess their functional characterization, the two ORFs were cloned and overexpressed in E. coli. The pTsbg enzyme had activity towards o-Nitrophenyl-β-d-galactopyranoside (ONPG) and p-Nitrophenyl-β-d-fucopyranoside, with high thermal stability and showing maximal activity at 85 °C and pH 6, nevertheless the enzyme failed to hydrolyze lactose. The other enzyme, Tsbg, was unable to hydrolyze even ONPG or lactose. This finding highlights the challenge of finding novel active enzymes based only on their sequence.

Download Full-text

Biothermodynamics and calorimetric methods

Pure and Applied Chemistry ◽

10.1351/pac198855030515 ◽

1983 ◽

Vol 55 (3) ◽

pp. 515-528 ◽

Cited By ~ 13

Author(s):

I. Wadsö

Keyword(s):

Calorimetric Methods

Download Full-text

Kinetics of Na+/H+ exchange in vascular smooth muscle cells from WKY and SHR: effects of phorbol ester

AJP Cell Physiology ◽

10.1152/ajpcell.1995.268.1.c14 ◽

1995 ◽

Vol 268 (1) ◽

pp. C14-C20 ◽

Cited By ~ 19

Author(s):

G. Hoffmann ◽

Y. Ko ◽

A. Sachinidis ◽

B. O. Gobel ◽

H. Vetter ◽

...

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Muscle Cells ◽

Maximal Activity ◽

Hill Coefficient ◽

Kinetic Properties ◽

Wistar Kyoto ◽

Kinetics Of

The kinetic properties of Na+/H+ exchange were investigated in vascular smooth muscle cells (VSMC) in culture from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Antiport activity was measured in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein-loaded cells after nigericin-induced cytosolic acidification. Studies were performed without (control) and with pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA; 200 nM). Na+/H+ exchange markedly differed between the two strains with lower Hill coefficients [1.56 +/- 0.17 (SE) vs. 2.62 +/- 0.36] and higher maximal activity (Vmax) values (55.85 +/- 5.24 vs. 31.11 +/- 2.38 mmol H+.l-1.min-1) in SHR compared with WKY cell lines. PMA markedly altered the antiport kinetics in WKY VSMC with a decrease in the Hill coefficient (1.75 +/- 0.14) without affecting Vmax (31.88 +/- 1.55 mmol H+.l-1.min-1). In VSMC from SHR, PMA had no effect on the kinetic variables investigated. Thus two kinetic abnormalities are present with respect to Na+/H+ antiport activity in VSMC from SHR compared with WKY, i.e., increased Vmax and decreased Hill coefficient. The observation that PMA does not affect the kinetics of the Na+/H+ antiport in VSMC from SHR suggests a marked degree of antiporter prestimulation in this animal model of genetic hypertension.

Download Full-text

Effect of acidosis on PTH-dependent renal adenylate cyclase in phosphorus deprivation: role of G proteins

AJP Renal Physiology ◽

10.1152/ajprenal.1990.258.6.f1640 ◽

1990 ◽

Vol 258 (6) ◽

pp. F1640-F1649

Author(s):

E. Bellorin-Font ◽

R. Starosta ◽

C. L. Milanes ◽

C. Lopez ◽

N. Pernalete ◽

...

Keyword(s):

Metabolic Acidosis ◽

Adenylate Cyclase ◽

Maximal Activity ◽

Phosphate Deprivation ◽

Adp Ribosylation ◽

Phosphate Depletion ◽

Cortical Membranes ◽

And Function ◽

Gs Alpha

These studies examine the regulation of adenylate cyclase in renal cortical membranes from phosphate-deprived and phosphate-deprived acidotic dogs. Enzyme stimulation by parathyroid hormone (PTH) was decreased in phosphate deprivation [Vmax 1,578 +/- 169 vs. 2,581 +/- 219 pmol adenosine 3',5'-cyclic monophosphate (cAMP).mg protein-1 x 30 min-1 in controls, P less than 0.01]. Metabolic acidosis further decreased PTH-stimulated activity. Membranes from phosphate-deprived dogs showed a decrease in Gs alpha-content by cholera toxin-dependent ADP-ribosylation (174 +/- 18 arbitrary units vs. 266.4 +/- 13.6 in controls, P less than 0.01). Metabolic acidosis further decreased Gs alpha-content, P less than 0.01. Gi content by pertussis-dependent ADP-ribosylation was also lower in phosphate-deprived and phosphate-deprived acidotic animals. Gs function was examined by its property to protect the catalytic unit from inactivation by N-ethylmaleimide when preincubated with GTP gamma S. In controls, protection of inactivation was 80% of the maximal activity, whereas in phosphate deprivation protection was less than 50%. In conclusion, metabolic acidosis enhances adenylate cyclase resistance to PTH in phosphate deprivation. These alterations are associated with a decrease in the content and function of Gs alpha, suggesting a role of Gs in the renal adaptation to phosphate depletion and acidosis.

Download Full-text

Enzymic characterization in vitro of recombinant proprotein convertase PC4

Biochemical Journal ◽

10.1042/bj3430029 ◽

1999 ◽

Vol 343 (1) ◽

pp. 29-37 ◽

Cited By ~ 16

Author(s):

Ajoy BASAK ◽

Bakary B. TOURÉ ◽

Claude LAZURE ◽

Majambu MBIKAY ◽

Michel CHRÉTIEN ◽

...

Keyword(s):

Synthetic Peptides ◽

Serine Proteases ◽

Active Form ◽

Molecular Size ◽

Maximal Activity ◽

Transition Metal Ions ◽

Proprotein Convertase ◽

Major Band ◽

Insulin Growth Factor

Proprotein convertase PC4A, a member of the subtilisin/kexin family of serine proteases, was obtained in enzymically active form following expression of vaccinia virus recombinant rat (r)PC4A in GH4C1 cells. It displayed maximal activity at pH 7.0 and a Ca2+ concentration of 2.0 mM. Using PC4-specific antibodies, Western blot analysis of the medium revealed a major band at ≈ 54 kDa, corresponding to the molecular size of mature rPC4A. Among the various peptidyl-[4-methylcoumarin 7-amide (MCA)] substrates tested, the one that was preferred the most by rPC4A was acetyl (Ac)-Arg-Lys-Lys-Arg-MCA, which is cleaved 9 times faster (as judged from Vmax/Km measurements) than the best furin and PC1 substrate, pGlu-Arg-Thr-Lys-Arg-MCA. Recombinant rPC4A, along with human (h)furin and hPC1, cleaved a 17-amino-acid synthetic peptide, YQTLRRRVKR↓ SLVVPTD (where ↓ denotes site of cleavage, and the important basic residues are shown in bold), encompassing the junction between the putative pro-segment of rPC4A and the active enzyme, suggesting a possible auto-activation of the enzyme. In an effort to identify potential physiological substrates for PC4, studies were performed with pro-[insulin-growth-factor (IGF)]-derived synthetic peptides, namely Ac-PAKSAR↓ SVRA (IGF-I66-75) and Ac-PAKSER↓ DVST (IGF-II63-72), as well as two lysine mutants [(IGF-I66-75Lys70) and (IGF-II63-72Lys67)]. Unlike PC1 and furin, rPC4A cleaved efficiently both IGF-I66-75 and IGF-II63-72, suggesting a possible role of PC4 in the maturation of IGF-I and -II. In contrast, the peptides with a position 2 (P2) lysine mutation, IGF-I66-75Lys70 and IGF-II63-72Lys67, were cleaved more efficiently by PC1 and furin compared with rPC4A. Furthermore, using synthetic peptides containing the processing sites of pituitary adenylate-cyclase-activating polypeptide (PACAP)-38, we were able to confirm that, of the two testicular enzymes PC4 and PC7, PC4 is the best candidate enzyme for maturation of PACAP. Our data suggest that rPC4A is a functionally active convertase, with a substrate specificity somewhat different from that of other convertases, namely KXXR↓ (where X denotes any other residue). As expected, p-chloromercuribenzoic acid and metal chelators such as EDTA, EGTA and trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid inhibit the proteolytic activity of rPC4A, whereas it is activated by dithiothreitol. PC4A was also inhibited by transition-metal ions (Cu2+>Hg2+>Zn2+ Ni2+>Co2+), as well as by small peptide semicarbazones (SCs), such as Arg-Lys-Lys-Arg-SC (Ki 0.75 μM) and Arg-Ser-Lys-Arg-SC (Ki 11.4 μM).

Download Full-text

Human replication-dependent histone H3 genes are activated by a tandemly arranged pair of two CCAAT boxes

Biochemical Journal ◽

10.1042/bj20040502 ◽

2004 ◽

Vol 384 (2) ◽

pp. 317-326 ◽

Cited By ~ 5

Author(s):

Heiner KOESSLER ◽

Joerg KAHLE ◽

Christa BODE ◽

Detlef DOENECKE ◽

Werner ALBIG

Keyword(s):

Electrophoretic Mobility Shift Assay ◽

Electrophoretic Mobility ◽

Histone H3 ◽

Maximal Activity ◽

Significant Loss ◽

Tata Box ◽

Mobility Shift ◽

Nuclear Factor Y ◽

Binding Factor ◽

Mobility Shift Assay

We have analysed the transcriptional regulation of the human histone H3 genes using promoter deletion series, scanning mutagenesis, specific mutagenesis and electrophoretic mobility-shift assay experiments. The promoters of five of the six examined histone H3 genes showed near-maximal activity at lengths of 133–227 bp: H3/d 198 bp, H3/h 147 bp, H3/k 133 bp, H3/m 227 bp, H3/n 140 bp (exception H3/i). To search for functional cis-elements within these regions, we performed scanning mutagenesis of the two histone H3 promoters H3/k and H3/m. Mutagenesis revealed that the functional framework of the histone H3 promoters consists of a TATA box and two tandemly arranged CCAAT boxes in relatively fixed positions. Alterations of the distance between the CCAAT boxes and of the distance between the CCAAT boxes and the TATA box resulted in significant loss of activity. In electrophoretic mobility-shift assay experiments, the factor CBF (CCAAT-binding factor)/NF-Y (nuclear factor-Y) bound to isolated CCAAT boxes of the H3/k promoter. This suggests that an initiation complex is formed on the histone H3 promoter that has a defined structure and limited flexibility, consisting of two molecules of CBF/NF-Y and further (general or specific) transcription factors.

Download Full-text

Identification and characterization of Sulfolobus solfataricusD-gluconate dehydratase: a key enzyme in the non-phosphorylated Entner–Doudoroff pathway

Biochemical Journal ◽

10.1042/bj20041053 ◽

2005 ◽

Vol 387 (1) ◽

pp. 271-280 ◽

Cited By ~ 58

Author(s):

Seonghun KIM ◽

Sun Bok LEE

Keyword(s):

Molecular Mass ◽

Gel Filtration ◽

Maximal Activity ◽

Genome Database ◽

Sds Page ◽

Key Enzyme ◽

Bivalent Metal Ions ◽

Ammonium Sulphate Fractionation ◽

Identification And Characterization

The extremely thermoacidophilic archaeon Sulfolobus solfataricus utilizes D-glucose as a sole carbon and energy source through the non-phosphorylated Entner–Doudoroff pathway. It has been suggested that this micro-organism metabolizes D-gluconate, the oxidized form of D-glucose, to pyruvate and D-glyceraldehyde by using two unique enzymes, D-gluconate dehydratase and 2-keto-3-deoxy-D-gluconate aldolase. In the present study, we report the purification and characterization of D-gluconate dehydratase from S. solfataricus, which catalyses the conversion of D-gluconate into 2-keto-3-deoxy-D-gluconate. D-Gluconate dehydratase was purified 400-fold from extracts of S. solfataricus by ammonium sulphate fractionation and chromatography on DEAE-Sepharose, Q-Sepharose, phenyl-Sepharose and Mono Q. The native protein showed a molecular mass of 350 kDa by gel filtration, whereas SDS/PAGE analysis provided a molecular mass of 44 kDa, indicating that D-gluconate dehydratase is an octameric protein. The enzyme showed maximal activity at temperatures between 80 and 90 °C and pH values between 6.5 and 7.5, and a half-life of 40 min at 100 °C. Bivalent metal ions such as Co2+, Mg2+, Mn2+ and Ni2+ activated, whereas EDTA inhibited the enzyme. A metal analysis of the purified protein revealed the presence of one Co2+ ion per enzyme monomer. Of the 22 aldonic acids tested, only D-gluconate served as a substrate, with Km=0.45 mM and Vmax=0.15 unit/mg of enzyme. From N-terminal sequences of the purified enzyme, it was found that the gene product of SSO3198 in the S. solfataricus genome database corresponded to D-gluconate dehydratase (gnaD). We also found that the D-gluconate dehydratase of S. solfataricus is a phosphoprotein and that its catalytic activity is regulated by a phosphorylation–dephosphorylation mechanism. This is the first report on biochemical and genetic characterization of D-gluconate dehydratase involved in the non-phosphorylated Entner–Doudoroff pathway.

Download Full-text

Evidence that coated vesicles isolated from brain are calcium-sequestering organelles resembling sarcoplasmic reticulum.

The Journal of Cell Biology ◽

10.1083/jcb.75.1.135 ◽

1977 ◽

Vol 75 (1) ◽

pp. 135-147 ◽

Cited By ~ 130

Author(s):

A L Blitz ◽

R E Fine ◽

P A Toselli

Keyword(s):

Sarcoplasmic Reticulum ◽

Calcium Ions ◽

Adenosine Triphosphatase ◽

Sodium Dodecyl ◽

Maximal Activity ◽

Coated Vesicles ◽

Potassium Oxalate ◽

Triton X ◽

Trapping Agent ◽

The Brain

Coated vesicles from the brain have been purified to near morphological homogeneity by a modification of the method of Pearse. These vesicles resemble sarcoplasmic reticulum fragments isolated from skeletal muscle. They contain proteins with 100,000- and 55,000-dalton mol wt which co-migrate on polyacrylamide gels, in the presence of sodium dodecyl sulfate, with the two major proteins of the sarcoplasmic reticulum fragment. These vesicles contain adenosine triphosphatase (ATPase) activity which is stimulated by calcium ions in the presence of Triton X-100 (Rohm & Haas Co., Philadelphia, Pa.), displaying maximal activity at 8 x 10(-7) M Ca ++. They take up calcium ions from the medium, and this uptake is stimulated by ATP and by potassium oxalate, a calcium-trapping agent. The 100,000-dalton protein of the coated vesicles displays immunological reactivity with an antiserum directed against the 100,000-dalton, calcium-stimulated ATPase of the sarcoplasmic reticulum. As with the sarcoplasmic reticulum fragment, this protein becomes radiolabeled when coated vesicles are briefly incubated with gamma-labeled [32P]ATP. The possible functions of coated vesicles as calcium-sequestering organelles are discussed.

Download Full-text