Protochlorophyllide reductase. 1. Determination of the regiochemistry and the stereochemistry of the reduction of protochlorophyllide to chlorophyllide
- Cornell Univ., Ithaca, NY (USA)
It has been estimated that over 1 billion tons of chlorophyll are synthesized in the biosphere each year. Although the chlorophyll biosynthetic pathway has been the subject of intense investigation over the 50 years, much remains to be discovered. One promising area of investigation is the remarkable color change, from yellow to green, that occurs when dark-grown plants are exposed to light. This greening reaction involves the reduction of protochlorophyllide to chlorophyllide and is a key regulatory step both in the biosynthesis of chlorophyll and in the development of the chloroplast. This reaction is catalyzed by the enzyme protochlorophyllide reductase and is of interest because it is one of only two known light-requiring enzymatic reactions. The enzyme has been purified from oats, barley, wheat, and squash. It is an unstable membrane-bound protein of 37,000 D molecular weight. The quantum yield for protochlorophyllide reduction in barley seedlings is 0.4 and the action spectrum for the reaction in corn seedlings follows the absorption spectrum of protochlorophyllide. As the first step in our mechanistic investigation of this important reaction, we have determined the regiochemistry and the stereochemistry of the reduction catalyzed by the oats enzyme. On the basis of this information, we propose a model for the active site of the enzyme.
- OSTI ID:
- 5330010
- Journal Information:
- Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 111:8; ISSN 0002-7863; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
CARBOXYLIC ACIDS
CATALYSIS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHLOROPHYLL
DATA
ENZYMES
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
REDUCTION
STEREOCHEMISTRY
SYNTHESIS