Hydrolysis of Leaf Fraction 1 Protein by the Proteolytic Rumen Bacterium Bacteroides ruminicola R8/4

Abstract

Proteolytic activity in a batch culture of B. ruminicola R8/4 (a rumen bacterium of ruminants) was maximal and largely (> 90%) cell-associated during the mid-exponential phase of growth. The cell-bound protease was not inactivated during storage at -70.degree. C and was not significantly affected by pH 5.9-8.2, but was subject to substrate inhibition by leaf Fraction 1 protein (from lucerne) (ribulose-1,5-bisphosphate carboxylase; EC 4.1.1.39) and was most active in the presence of thiol reagents. Radioactive Fraction 1 protein was hydrolyzed by nongrowing and growing cells of B. ruminicola R8/4 with the production of peptides and free amino acids. Deaminase activity was absent. Radioactive amino acids were incorporated into bacterial proteins from [14C]Fraction 1 protein without substantial change in specific radioactivity.