PROPERTIES OF PROTEINASE FROMSTREPTOCOCCUS FAECALISVAR.LIQUEFACIENS

Bleiweis, ArnoldS. (The Pennsylvania State University, University Park),and Leonard N. Zimmerman. Properties of proteinase fromStreptococcus faecalisvar.liquefaciens. J. Bacteriol.88:653–659. 1964.—The extracellular group D streptococcal proteinase is inactivated by chelating agents [ethylenediamine-tetraacetate (EDTA),o-phenanthroline, and 8-quinolinol] and mercaptans (cysteine, mercaptoethanol, and thioglycolate). The optimal inhibitory concentrations of EDTA (4 × 10−4m) and cysteine (2.5 × 10−2m) promote rapid loss of activity with 50% inactivation after 4 to 5 min. Enzyme inactivated by either EDTA or cysteine is reactivated about 80% by 4 × 10−4mZn++. Such reactivation of EDTA-treated enzyme is prevented completely by iodoacetate (5 × 10−2m) and of cysteine-treated enzyme by oxidizing conditions, which suggests that the zinc binding-site may be a thiol. High levels of zinc (10−3m) do not allow reactivation in either case, and actually inhibit native proteinase. Ca++, Mg++, Co++, Fe++, Cu++, and Ni++do not reactivate cysteine-treated enzyme, but Mn++(10−4to 8 × 10−4m) allows 27% reversal. N2-held, cysteine-treated enzyme can be spontaneously reactivated if the substrate is flushed with O2during the assay; leakage of air or O2into the samples before assay leads to loss of reactivatability. Native proteinase does not lose activity after dialysis for 43 hr against 0.07mphosphate buffer. It is concluded that the group D proteinase obtained fromStreptococcus faecalisvar.liquefaciensis probably a zinc metalloenzyme that is unlike the thiol-activated, group A streptococcal proteinase, but similar to the mammalian carboxypeptidase A.