Studies on the active centre(s) of rat liver porphyrinogen carboxy-lyase. In vivo effect of hexachlorobenzene on decarboxylation site(s) of porphyrinogens.
1. The role of histidine on the decarboxylation of porphyrinogens of 7-, 6-, and 5-COOH III brought about by porphyrinogen carboxy-lyase (PCL) was studied. 2. For this purpose hepatic PCL from normal and hexachlorobenzene (HCB) treated rats were modified with diethylpyrocarbonate. 3. The results indicated that the enzyme from both normal and porphytic animals had histidine at the binding sites of all the porphyrinogens assayed. 4. Comparative studies between the enzyme from normal and porphyric rats suggested that in vivo HCB treatment affected the active site for the decarboxylation of 7-, 6- and 5-COOH porphyrinogens III at histidine residues. 5. On the other hand arginine modification by 2,3-butanedione treatment altered 5-COOH porphyrinogen III decarboxylation for both enzymes. However this amino acid was not involved at the binding site of this substrate.
Departamento de Quimica Biologica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
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Billi de Catabbi
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San Martin de Viale
D000818:Animals; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry / Q000378:metabolism*; D003653:Decarboxylation; D003931:Diacetyl / Q000494:pharmacology; D005260:Female; D006581:Hexachlorobenzene / Q000633:toxicity; D006639:Histidine / Q000737:chemistry; D008099:Liver / Q000201:enzymology*; D011164:Porphyrias / Q000139:chemically induced / Q000201:enzymology; D011165:Porphyrinogens / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar
D011165:Porphyrinogens; D006639:Histidine; D006581:Hexachlorobenzene; D001120:Arginine; D002262:Carboxy-Lyases; C022430:porphyrinogen carboxy-lyase; D003931:Diacetyl