Chlorophyll a biosynthesis

1976 ◽  
Vol 273 (924) ◽  
pp. 207-225 ◽  
Keyword(s):  
Chlorophyll A ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Synthesis Reaction ◽  
Etiolated Leaves ◽  
Regulatory Aspects ◽  
Vinyl Group ◽  
Chlorophyll A Biosynthesis ◽  
Monomethyl Ester

Protoporphyrin IX is believed to be an intermediate common to both haem and chlorophyll biosynthesis. The pathway specific to chlorophyll starts with magnesium protoporphyrin and its monomethyl ester. Two routes have been proposed for conversion of the latter compound to protochlorophyllide: A, formation of the isocyclic ring followed by reduction of the 4-vinyl group, or B, reduction of the 4-vinyl group followed by formation of the isocyclic ring. Membranes prepared from isolated barley etioplasts are found to convert magnesium 2,4-divinylphaeoporphyrin a 5 monomethyl ester to chlorophyllide a at a rate equal to that of chlorophyll synthesis in intact leaves: this result supports route A. NADPH is necessary to maintain the two successive reductive steps: reduction of the 4-vinyl group and then the photoreduction of ring IV to yield chlorophyllide. The prohaem content of etiolated leaves does not increase during the phase of active chlorophyll synthesis although evidence is presented that suggests that the ALA synthesis reaction that regulates chlorophyll synthesis is common to both pathways. This and other regulatory aspects are discussed.

scholarly journals Photosystem Disorder Could be the Key Cause for the Formation of Albino Leaf Phenotype in Pecan

2020 ◽  
Vol 21 (17) ◽  
pp. 6137
Author(s):  
Ji-Yu Zhang ◽  
Tao Wang ◽  
Zhan-Hui Jia ◽  
Zhong-Ren Guo ◽  
Yong-Zhi Liu ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Molecular Mechanisms ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Photosynthetic Electron Transport ◽  
Chlorophyll Degradation ◽  
Pheophorbide A ◽  
Leaf Phenotype ◽  
Photosynthesis Pathway ◽  
Almost All

Pecan is one of the most famous nut species in the world. The phenotype of mutants with albino leaves was found in the process of seeding pecan, providing ideal material for the study of the molecular mechanisms leading to the chlorina phenotype in plants. Both chlorophyll a and chlorophyll b contents in albino leaves (ALs) were significantly lower than those in green leaves (GLs). A total of 5171 differentially expression genes (DEGs) were identified in the comparison of ALs vs. GLs using high-throughput transcriptome sequencing; 2216 DEGs (42.85%) were upregulated and 2955 DEGs (57.15%) were downregulated. The expressions of genes related to chlorophyll biosynthesis (HEMA1, encoding glutamyl-tRNA reductase; ChlH, encoding Mg-protoporphyrin IX chelatase (Mg-chelatase) H subunit; CRD, encoding Mg-protoporphyrin IX monomethylester cyclase; POR, encoding protochlorophyllide reductase) in ALs were significantly lower than those in GLs. However, the expressions of genes related to chlorophyll degradation (PAO, encoding pheophorbide a oxygenase) in ALs were significantly higher than those in GLs, indicating that disturbance of chlorophyll a biosynthesis and intensification of chlorophyll degradation lead to the absence of chlorophyll in ALs of pecan. A total of 72 DEGs associated with photosynthesis pathway were identified in ALs compared to GLs, including photosystem I (15), photosystem II (19), cytochrome b6-f complex (3), photosynthetic electron transport (6), F-type ATPase (7), and photosynthesis-antenna proteins (22). Moreover, almost all the genes (68) mapped in the photosynthesis pathway showed decreased expression in ALs compared to GLs, declaring that the photosynthetic system embedded within the thylakoid membrane of chloroplast was disturbed in ALs of pecan. This study provides a theoretical basis for elucidating the molecular mechanism underlying the phenotype of chlorina seedlings of pecan.

scholarly journals Xantha-l encodes a membrane subunit of the aerobic Mg-protoporphyrin IX monomethyl ester cyclase involved in chlorophyll biosynthesis

2005 ◽  
Vol 102 (16) ◽  
pp. 5886-5891 ◽  
Author(s):  
K. Rzeznicka ◽  
C. J. Walker ◽  
T. Westergren ◽  
C. G. Kannangara ◽  
D. von Wettstein ◽  
...  
Keyword(s):  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Monomethyl Ester

scholarly journals Yellow-Leaf 1 encodes a magnesium-protoporphyrin IX monomethyl ester cyclase, involved in chlorophyll biosynthesis in rice (Oryza sativa L.)

PLoS ONE ◽  
2017 ◽  
Vol 12 (5) ◽  
pp. e0177989 ◽  
Author(s):  
Zhonghua Sheng ◽  
Yusong Lv ◽  
Wei Li ◽  
Rongjian Luo ◽  
Xiangjin Wei ◽  
...  
Keyword(s):  
Oryza Sativa ◽  
Oryza Sativa L ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Yellow Leaf ◽  
Monomethyl Ester

scholarly journals The magnesium-insertion step of chlorophyll biosynthesis is a two-stage reaction

1994 ◽  
Vol 299 (1) ◽  
pp. 277-284 ◽  
Author(s):  
C J Walker ◽  
J D Weinstein
Keyword(s):  
Room Temperature ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Complete Loss ◽  
Second Step ◽  
Activation Effect ◽  
Low Protein ◽  
Pisum Sativum L ◽  
Activated State

Mg(2+)-chelatase catalyses the first step unique to chlorophyll synthesis, namely the insertion of Mg2+ into protoporphyrin IX. When pea (Pisum sativum L., cv. Spring) chloroplasts are lysed in a buffer lacking Mg2+ and the thylakoids removed by centrifugation, the remaining mixture of light membranes and soluble proteins (LM/S) has high Mg(2+)-chelatase activity. Several lines of evidence are presented to show that the Mg2+ insertion catalysed by this preparation is a two-step reaction consisting of activation followed by Mg2+ chelation. An activated state of Mg(2+)-chelatase is achieved by preincubating LM/S with ATP. The activated state is observed as the elimination of the approx. 6 min lag in the rate of Mg2+ chelation on addition of the porphyrin substrate. The activity of LM/S assayed at low protein concentrations can be greatly enhanced by preincubating at high protein concentrations (12 mg/ml is optimal). This activation effect requires the presence of both LM and S fractions, as well as ATP. Both steps require ATP, but at different concentrations; the first step is optimal at > 0.5 mM (EC50 = 0.3 mM) and the second step is optimal at 0.3 mM (EC50 < 0.2 mM). ATP in the first step could be replaced by ATP[S]; this analogue could not sustain activity in the second step. This activated state was stable for at least 30 min at room temperature, but chilling of preincubated LM/S on ice for 30 min caused an almost complete loss of the activated state.

Studies on the biosynthesis of the Chlorobium chlorophylls

1976 ◽  
Vol 273 (924) ◽  
pp. 255-276 ◽  
Keyword(s):  
Methyl Ester ◽  
Chlorophyll A ◽  
Alkyl Group ◽  
Biosynthetic Pathway ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Methyl Groups ◽  
Chemical Transformations ◽  
The Novel ◽  
Feeding Experiments

The Chlorobium chlorophylls (660) from Chloropseudomonas ethylicum are shown by 13 C n.m.r. spectroscopy and certain chemical transformations to be meso -methylated at the δ-position. Earlier work, which proposed that the meso -alkyl group was present at the α or β positions, is shown to be experimentally correct, but incorrectly interpreted. On the basis of 14 C and 13 C feeding experiments, the novel methyl groups in the (660) chlorophylls are shown to be derived from methionine in all cases. For most of the homologous mixture of (660) chlorophylls, the branch point from the biosynthetic pathway to chlorophyll a appears to lie between uroporphyrinogen III and coproporphyrinogen III; earlier workers had suggested that Chlorobium chlorophyll biosynthesis proceeded through magnesium protoporphyrin IX mono-methyl ester and possibly also via bacteriochlorophyll a or one of its immediate precursors. Evidence against this proposal, and a working hypothesis explaining feeding results, is presented. On the basis of this hypothesis, proposals for the structures of certain fractions of the (660) chlorophylls which are currently in dispute, are presented.

scholarly journals The use of continuous assays to characterize the oxidative cyclase that synthesizes the chlorophyll isocyclic ring

1987 ◽  
Vol 243 (1) ◽  
pp. 23-29 ◽  
Author(s):  
A Nasrulhaq-Boyce ◽  
W T Griffiths ◽  
O T G Jones
Keyword(s):  
Dimethyl Ester ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Complexing Agents ◽  
Zinc Protoporphyrin ◽  
Iron Ions ◽  
Strong Inhibition ◽  
Dark Incubation ◽  
Inhibited Enzyme ◽  
Monomethyl Ester

A continuous spectroscopic assay has been developed for magnesium protoporphyrin monomethyl ester oxidative cyclase, which records either the dark formation of both free and protein-bound magnesium phaeoporphyrin or, following flash illumination, its corresponding chlorin. The properties of the enzyme were studied in wheat etioplasts. When plastids were pre-illuminated in the presence of NADPH all endogenous protochlorophyllide was converted into chlorophyllide and the product of dark incubation with magnesium protoporphyrin monomethyl ester was protein-bound magnesium 2-vinyl phaeoporphyrin a5 monomethyl ester with either a vinyl or an ethyl group at position 4 of the macrocycle alone. Rates of chlorin production from magnesium protoporphyrin monomethyl ester (up to 1240 pmol/h per mg of protein) were adequate to support known rates of plant chlorophyll synthesis. The enzyme required NADPH and O2 and had an approximate Km of 0.5 microM for magnesium protoporphyrin IX monomethyl ester. Lipid-soluble metal-complexing agents inhibited enzyme activity: hydrophilic agents were ineffective. The strong inhibition of mycobactin suggested the involvement of iron ions. Zinc protoporphyrin monomethyl ester, but not copper or nickel or metal-free protoporphyrin monomethyl esters, was a substrate; magnesium protoporphyrin dimethyl ester was inhibitory. The activity of the enzyme was unchanged by prior greening of the plants. The activity in isolated etioplasts was very dependent upon intactness of the plastid structure.

The catalytic subunit of magnesium-protoporphyrin IX monomethyl ester cyclase forms a chloroplast complex to regulate chlorophyll biosynthesis in rice

2016 ◽  
Vol 92 (1-2) ◽  
pp. 177-191 ◽  
Author(s):  
Weiyi Kong ◽  
Xiaowen Yu ◽  
Haiyuan Chen ◽  
Linglong Liu ◽  
Yanjia Xiao ◽  
...  
Keyword(s):  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Catalytic Subunit ◽  
Monomethyl Ester
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