Protease inhibitors but not proteases inhibit the glucose-6-phosphatase of native rat liver microsomes.
Controlled proteolytic digestion by trypsin or bacterial proteases limited to the cytosolic side of the native microsomal membrane is not efficient to inhibit glucose-6-phosphate hydrolysis. Modification of the microsomes with deoxycholate prior to protease treatment is prerequisite to allow accessibility of the integral protein and inhibition of enzyme activity. Glucose-6-phosphatase of native microsomes, however, is rapidly inactivated by micromolar concentrations of TPCK as well as TLCK. In deoxycholate-modified microsomes both reagents do not affect glucose-6-phosphate hydrolysis. These results indicate that in the native, intact microsomal membrane glucose-6-phosphatase is not accessible to proteolytic attack from the cytoplasmic surface. The putative inhibitory effect of some trypsin or bacterial protease preparations on glucose-6-phosphatase of native microsomes observed most possibly is a result of contaminating agents as TPCK or TLCK.
Speth
M
M
Biochemisches Institut am Klinikum Justus-Liebig-Universität, Giessen, FRG.
Schulze
H U
HU
D000818:Animals; D010450:Endopeptidases / Q000494:pharmacology*; D005952:Glucose-6-Phosphatase / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010088:Oxidoreductases / Q000737:chemistry / Q000187:drug effects; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000187:drug effects; D011480:Protease Inhibitors / Q000494:pharmacology*; D011487:Protein Conformation; D051381:Rats; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism
D011480:Protease Inhibitors; D014107:Tosyllysine Chloromethyl Ketone; D014108:Tosylphenylalanyl Chloromethyl Ketone; D010088:Oxidoreductases; C020666:glutathione dehydrogenase (ascorbate); C023553:mannose-6-phosphatase; D010744:Phosphoric Monoester Hydrolases; D005952:Glucose-6-Phosphatase; D010450:Endopeptidases; D014357:Trypsin