The mechanism of inhibition by 2,2'-pyridylisatogen tosylate of NADPH-linked enzyme activities in microsomes isolated from rat liver.
Microsomal preparations isolated from rat liver were used to study the action of 2.2'-pyridylisatogen tosylate (PIT) on aniline hydroxylation, cytochrome c reduction and NADPH oxidation. PIT was found to inhibit both the NADPH-dependent (5-100 microM, PIT) and the NADPH-independent (0.05-2.5 mM, PIT) hydroxylation of aniline, but had no significant effect on either the NADPH-dependent oxidation of hexobarbital, or the NADPH-independent hydrolysis of glucose-6-phosphatase. PIT was also found to inhibit cytochrome c reductase competitively (Ki = 35 microM) and to stimulate NADPH oxidation (ED50 = 6.5 microM) PIT and aniline were both found to bind to the microsomal haemoprotein cytochrome P-450 and produce Type II spectral changes. It is proposed that PITs ability to bind to the haemoprotein and its ability to accept electrons from the microsomal NADPH-cytochrome c reductase system leads to the inhibition of aniline hydroxylase activity.
Cameron
I
I
Ashraf
A J
AJ
Markham
A
A
Sweetman
A J
AJ
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors*; D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors; D000815:Aniline Hydroxylase / Q000037:antagonists & inhibitors; D000818:Animals; D005952:Glucose-6-Phosphatase / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D007510:Isatin / Q000031:analogs & derivatives / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009249:NADP / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007211:Indoles; D009249:NADP; C009128:2,2'-pyridylisatogen tosylate; D007510:Isatin; D000255:Adenosine Triphosphate; D000429:Alcohol Oxidoreductases; C021353:hexobarbital oxidase; D000815:Aniline Hydroxylase; D005952:Glucose-6-Phosphatase