Differences in the binding of substrates to cytochromes P-450b and P-450e from rat liver microsomes.
Two phenobarbital-induced isoenzymes of the rat cytochrome P-450 have been isolated using a modification of a method described earlier. Titration of cytochromes P-450 with different compounds (followed by changes in the second derivative spectrum in the near ultraviolet region) reveals that tyrosyl residues are affected. These residues behave differently in the isoenzymes P-450b and P-450e. In the former, after addition of a substrate the tyrosyl residues become hidden in the nonpolar parts of the protein; however, then become accessible with increasing substrate concentration. In the latter, the exposure to a polar medium decreases with increasing substrate concentration.
Sebestian
J
J
Department of Microbiology, Charles University, Prague, Czechoslovakia.
Anzenbacher
P
P
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D013053:Spectrophotometry
D003577:Cytochrome P-450 Enzyme System; D010634:Phenobarbital