Mobilization of Stored Seed Reserves
7.6. STORED PROTEIN CATABOLISM
7.6.1. General Catabolism
Hydrolysis of storage protein (polypeptides) to their constituent amino acids requires a class of enzymes called proteinases, some of which effect total hydrolysis whereas others produce small polypeptides that must be degraded further by peptidases. The proteinases can be categorized in relation to the manner in which they hydrolyze their substrates as follows:
1. Endopeptidases: these cleave internal peptide bonds to yield smaller polypeptides.
2. Aminopeptidases: these sequentially cleave the terminal amino acid from the free amino end of the polypeptide chain.
3. Carboxypeptidases: as (2), but single amino acids are sequentially hy-drolyzed from the carboxyl end of the chain.