Induction of a novel Ca2+-dependent chymotrypsin-like serine protease by tumor promoters in rat livers.
Induction of a microsomal Ca2+-dependent serine protease by hepatic tumor promoters was studied. Male F344 rats were fed a diet containing one of the following promoting agents: phenobarbital (CAS: 50-06-6), dichlorophenyltrichloroethane (CAS: 50-29-3), butylated hydroxytoluene, ethyl-alpha-chlorophenoxyisobutyrate (CAS: 128-95-0), or 17-alpha-ethynylestradiol (CAS: 57-63-6) or a nonpromoting agent, diphenylhydantoin (CAS: 57-41-0), for 1 week. By treatment with promoters, the protease activity in the microsomal fraction was increased to threefold to fivefold that of control, whereas only a slight increase of activity was found after diphenylhydantoin treatment. The Ca2+-dependent protease activity was determined with the use of N-benzoyl-L-tyrosine ethyl ester as the substrate in a medium containing 50 mM CaCl2 for its maximal activity. This protease was preferentially localized in the smooth microsomal membrane and strongly inhibited by diisopropyl phosphorofluoridate (CAS: 55-91-4), and the optimum pH of the activity was 7.8. It appears that the Ca2+-dependent serine protease measured by using a chymotrypsin substrate is a novel protease, and induction of its activity by hepatic tumor-promoting agents is a common and specific phenomenon.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002273:Carcinogens / Q000494:pharmacology*; D002850:Chromatography, Gel; D002918:Chymotrypsin / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D010450:Endopeptidases / Q000096:biosynthesis* / Q000302:isolation & purification; D004790:Enzyme Induction; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010634:Phenobarbital / Q000008:administration & dosage; D011506:Proteins / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D012697:Serine Endopeptidases
D002273:Carcinogens; D011506:Proteins; D003577:Cytochrome P-450 Enzyme System; D010450:Endopeptidases; D012697:Serine Endopeptidases; D002918:Chymotrypsin; D002118:Calcium; D010634:Phenobarbital