ISOLATION OF 2 DIPEPTIDE HYDROLASES FROM MOUSE-BRAIN CYTOSOL

Two dipeptide cleaving enzymes from mouse brain cytosol were purified in parallel by ammonium sulfate precipitation followed by ultrafiltration and chromatography on diethylaminoethyl cellulose and hydroxylapatite. The enzymes appeared as non-overlapping peaks during the final step. The purification attained was 431-fold for enzyme I and 61-fold for enzyme II. The latter, from its specificity, pH optimum, and inhibition by SH is similar to glycylleucine dipeptidase (IUB 3.4.13.2) from other mammalian sources. Purification of enzyme I has not been reported previously. It is inhibited by EDTA and o-phenanthroline and stimulated by SH. Typical substrates are Ala-Ala, Lys-Ala, Trp-Gly and Pro-Ala. Some activity was found against peptides with 3 or more residues but none against peptides containing acidic or D-amino acids. © 1979.