CASTANOSPERMINE ANALOGS - THEIR INHIBITION OF GLYCOPROTEIN PROCESSINGALPHA-GLUCOSIDASES FROM PORCINE KIDNEY AND B16F10 CELLS

We have used a simple and efficient procedure for the synthesis of N-5 -carboxypentyl-1-deoxynojirimycin, an affinity ligand for alpha-glucos idase I (Bernotas,R.C. and Ganem,B., Biochem, J., 270, 539-540, 1990), The affinity gel was used to purify alpha-glucosidase I in one step f rom crude extract, In subsequent steps, partially purified alpha-gluco sidase II was obtained, We have synthesized several analogues of casta nospermine and studied their inhibition of alpha-glucosidase I in vitr o using purified alpha-glucosidase I and in vivo in cultured B16F10 ce lls. Although the castanospermine analogues were significantly less ac tive against the purified enzyme (IC50 similar to 1-23 mu g/ml) as com pared to castanospermine (IC50 = 0.02 mu g/ml), several compounds had up to 30-fold higher activity than castanospermine against alpha-gluco sidase I in B16F10 cells, based on the accumulation of G(3)M(7-9)N(2) oligosaccharide-containing glycoproteins, These results suggest that t hese analogues with lipophilic side chains cross the membrane barrier more efficiently than castanospermine. Once inside the cell, they may be converted to their active metabolite, castanospermine, by cellular esterases to give enzyme inhibition.