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

作者: C J Walker , J D Weinstein

DOI: 10.1042/BJ2990277

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摘要: Mg(2+)-chelatase catalyses the first step unique to chlorophyll synthesis, namely insertion of Mg2+ into protoporphyrin IX. When pea (Pisum sativum L., cv. Spring) chloroplasts are lysed in a buffer lacking and thylakoids removed by centrifugation, remaining mixture light membranes soluble proteins (LM/S) has high activity. Several lines evidence presented show that catalysed this preparation is two-step reaction consisting activation followed chelation. An activated state achieved preincubating LM/S with ATP. The observed as elimination approx. 6 min lag rate chelation on addition porphyrin substrate. activity assayed at low protein concentrations can be greatly enhanced (12 mg/ml optimal). This effect requires presence both LM S fractions, well Both steps require ATP, but different concentrations; optimal > 0.5 mM (EC50 = 0.3 mM) second

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