Abstract
The soluble fraction from early bloom alfalfa herbage contained acid proteinase, neutral proteinase, carboxypeptidase and aminopeptidase activity. The pH profile of soluble proteinase activity with hemoglobin substrate indicated optima at pH 4.5 (acid proteinase) and 6.7 (neutral proteinase) with activities equivalent to 19.1 and 10.2 μmoles amino acid released h−1∙g−1, respectivity. Carboxypeptidase activity was optimal at pH 5.4 and corresponded to 165 μmoles amino acid released h−1∙g−1. Aminopeptidase activity was optimal at pH 6.5. Temperature profiles indicated a Q10 of 3.3 for the acid proteinase and 1.7 for the other hydrolytic enzymes. Maximal activities were recorded at 50 °C for the acid and neutral proteinases and at 40 °C for carboxypeptidase and aminopeptidase. All proteolytic enzymes were inhibited by PMSF (phenylmethylsulfonylfluoride). It was not possible to selectively inhibit only one type of proteinase or peptidase with the compounds tested. The results are discussed in relation to the ensiling of alfalfa herbage.
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