title: N-Alkylprotoporphyrin IX formation in 3,5-dicarbethoxy-1,4-dihydrocollidine-treated rats. Transfer of the alkyl group from the substrate to the porphyrin.
abstract: Administration of 3,5-dicarbethoxy-1,4-dihydrocollidine (DDC) to rats causes the accumulation of N-methylprotoporphyrin IX, a potent inhibitor of ferrochelatase. To clarify the origin of the porphyrin N-methyl group, we have synthesized and administered to rats N-ethyl-3,5-dicarbethoxy-1,4-dihydrocollidine (N-ethyl DDC) and 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine (DDEP), the DDC analogue with a 4-ethyl rather than 4-methyl group. Only N-methylprotoporphyrin IX is isolated from rats treated with the former agent, and only N-ethylprotoporphyrin IX from those treated with the latter. All four isomers of N-ethylprotoporphyrin IX are formed biologically. The structure of the isolated porphyrins has been confirmed by complete spectroscopic comparison with the four synthetic isomers of N-ethylprotoporphyrin IX. DDEP has been shown to cause NADPH- and time-dependent in vitro loss of hepatic microsomal cytochrome P-450. These results unequivocally establish that the 4-alkyl groups in DDC and dDEP are the source of the N-alkyl group in N-methyl- and N-ethylprotoporphyrin IX, respectively, and strongly suggest that the alkyl group is transferred to the prosthetic heme of cytochrome P-450 during catalytic processing of the substrate by the enzyme. The mechanism of the group transfer is discussed.
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003997:Dicarbethoxydihydrocollidine / Q000031:analogs & derivatives / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D011166:Porphyrins / Q000096:biosynthesis* / Q000138:chemical synthesis; D011524:Protoporphyrins / Q000096:biosynthesis*; D011725:Pyridines / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D011166:Porphyrins; D011524:Protoporphyrins; D011725:Pyridines; C030826:3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine; D003997:Dicarbethoxydihydrocollidine; C028842:N-methylprotoporphyrin IX; C030827:N-ethylprotoporphyrin IX; D003577:Cytochrome P-450 Enzyme System