title: Purification and Characterization of a Dipeptidase from Streptococcus cremoris Wg2.
abstract: A dipeptidase was purified to homogeneity from a crude cell extract of Streptococcus cremoris Wg2 by DEAE-Sephacel column chromatography followed by preparative disc gel electrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band with a molecular weight of 49,000. The dipeptidase is capable of hydrolyzing a range of dipeptides, but not peptides with longer chains. The enzyme was shown to be a metallo-Mn enzyme with a pH optimum of 8 and a temperature optimum of 50 degrees C. The enzyme is strongly inhibited by thiol-reducing reagents but not by sulfhydryl reagents. Kinetic studies indicated that the enzyme has a relatively low affinity for leucyl-leucine and alanyl-alanine (K(m), 1.6 and 7.9 mM, respectively) but can hydrolyze these substrates at very high rates (V(max), 3,700 and 13,000 mumol/min per mg of protein, respectively).
authors.affiliation: Department of Microbiology, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: van Boven
authors.forename: P S T
authors.initials: PS
authors.lastname: Tan
authors.forename: W N
authors.initials: WN
authors.lastname: Konings