Factors influencing the synthesis of an extracellular proteinase by Enterococcus faecalis subsp. liquefaciens

Abstract

Studies were conducted on optimum temperature, pH and the requirement for an energy source, amino acids, casein, Zn2+ and Ca2+ during the synthesis of an extracellular acid proteinase by Enterococcus faecalis var. liquefaciens. Synthesis was monitored using cells grown to mid-logarithmic phase and resuspended at high density in fresh growth medium. Proteinase production was optimal at 30 degrees C and pH 7.0. Proteinase synthesis, being energy-dependent, occurred only in glycolysing cells. The synthesis was high when lactose but not glucose was utilized as a source of energy, indicating that phospho-beta-galactosidase gene might probably be located directly upstream the proteinase gene on a plasmid. Good induction of proteinase synthesis could be achieved by 0.2-0.5% of either yeast extract or tryptic digested casein, perhaps due to its content of a wide variety of free amino acids. Casein was essential for preventing proteinase autolysis and sustaining the enzyme production. Zn2+ and Ca2+ were required for the formation of an active extracellular proteinase. The synthesis immediately ceased after addition of chloramphenicol or EDTA. EDTA inactivated the preformed proteinase as well. Sodium chloride at a concentration of 6.5% inhibited both proteinase synthesis and glycolysis.