Biosynthesis of y-Glutamylcysteine and Glutathione

As described in a number of recent reviews 219, 220, 221) the biosynthesis of glutathione in animals and microorganisms takes place by the following two reactions  

Partial purification of y-glutamylcysteine synthetase from bean seedlings (372, 373) and wheat germ (374) has been achieved. The general properties of these preparations are similar to those of the enzyme from animal sources, but no detailed specificity studies have been carried out. Ammonia or hydroxylamine could be used as substrates instead of cysteine but this may be caused by the presence of glutamine synthetase in the preparation. 

Glutathione synthetase is also present in Phaseolus vulgaris seedlings (372, 374) and the enzyme isolated from wheat germ has been partially purified (375). The enzyme from Phaseolus was not very specific for glycine which could be replaced by a number of other amino acids (374). 

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