Properties of Suc-GPLGP-MCAase and dipeptidyl-aminopeptidase in mouse calvaria-derived osteoblastic cells (MC3T3-E1).

In this study the properties of Suc-GPLGP-MCAase and dipeptidyl-aminopeptidase (DAP) in clone MC3T3-E1 cells which have osteoblastic ability were examined. The Suc-GPLGP-MCAase was the most active at pH 8.0 and its molecular weight was about 65,000 as judged by gel filtration method. The enzyme activity was increased by some metal ions such as Mn+2, Ca+2, and Mg+2 but inhibited by Zn+2 and Cu+2. EDTA increased the enzyme activity to 23-fold. The enzyme activity was slightly inhibited by thiol inhibitors, N-ethylmaleimide, and p-chloromercuribenzoic acid by 16% and 27%, respectively. The DAP has an optimum pH at 7.5, and a molecular weight of about 100,000. The enzyme was completely inhibited by diisopropylfuorophosphate, but not by N-ethylmaleimide, iodoacetic acid, p-chloromercuribenzoic acid, phenylmethylsulfonyl fluoride, EDTA, and several metals. These results show that Suc-GPLGP-MCAase and DAP in MC3T3-E1 cells have different novel properties compared with these enzymes in the peripheral tissues.