Inhibitors of Pig Kidney Trehalase

Trehazolin, a new trehalase inhibitor isolated from the culture broth of Micromonospora, was reported to be a highly specific inhibitor for porcine and silkworm trehalases with IC50 values of 5.5 × 10−9 and 3.7 × 10−9 M, respectively (O. Ando, H. Satake, K. Itoi, A. Sate, M. Nakajima, S. Takashi, H. Haruyama, Y. Ohkuma, T. Kinoshita, and R. Enokita (1991) J. Antibiot. 44, 1165-1168). We also found that trehazolin is a very powerful and quite specific inhibitor against purified pig kidney trehalase, giving an IC50 value of 1.9 × 10−8 M. Lineweaver-Burk plots showed that this compound was a competitive inhibitor of the trehalase. However, even at concentrations of 200 μg/ml, trehazolin did not inhibit the rat intestinal maltase or sucrase, yeast α-glucosidase or almond β-glucosidase. Validoxylamine A and vaiidamycin A, two other trehalase inhibitors, showed potent competitive inhibition against purified pig kidney trehalase, with IC50 values of 2.4 × 10−9 and 2.5 × 10−4 M, respectively. On the other hand, validoxylamine A was almost inactive against rat intestinal sucrase and maltase, with some inhibition being observed at millimolar concentration. A number of other glucosidase inhibitors, such as MDL 25637, castanospermine, and deoxynojirimycin were also tested against the purified trehalase and showed reasonable inhibitory activity.