Endopeptidase and Carboxypeptidase Enzymes of Vacuoles Prepared from Mesophyll Protoplasts of the Primary Leaf of Wheat Seedlings

Abstract

Vacuoles prepared from mesophyll protoplasts of the primary leaf of wheat (Triticum aestivum L. cv. Egret) contain carboxypeptidase (CP) and endopeptidase (EP) activity. CP activity was optimal at pH 5.2. The most preferred substrate was Z-Phe-Ala and activity against a wide range of other substrates was dependent on the C-terminal amino acid. Z-dipeptides with proline in any position were not hydrolysed. CP activity was inhibited by phenylmethylsulfonyl fluoride, diisopropylfluorophosphate, sodium dodecyl sulfate (SDS) and 4-hydroxymercuric benzoic acid. Thus the CP enzyme from the wheat leaf is a Serine Carboxypeptidase (EC 3.4.16). EP activity, assessed by following the degradation of the..