Seed germination studies. 3. Properties of a cell-free amino acid incorporating system from pea cotyledons; possible origin of cotyledonary alpha-amylase.

Pea cotyledonary alpha-amylase increases dramatically both in specific activity and total activity between days 7 to 10 when germination occurs in the dark. This enzymatic activity does not seem to appear as a consequence of release or formation of an activator, removal of an inhibitor, dissociation of an inactive amylase complex, or proteolytic decomposition of a zymogen precursor. The possibility remains that the alpha-amylase is newly synthesized during germination. The preparation and properties of a cell-free protein-synthesizing system from germinating pea cotyledons is described; polyuridylic acid must be added for l-phenylalanine incorporation. Active microsomal preparations can be obtained from cotyledons germinated 10 days.