AI Article Synopsis
- The study focused on how histidine affects the decarboxylation process of specific porphyrinogens by the enzyme porphyrinogen carboxy-lyase (PCL).
- Both normal and hexachlorobenzene (HCB) treated rats were compared, revealing that histidine is present at the binding sites for all tested porphyrinogens in both groups.
- Further analysis indicated that HCB treatment influenced histidine's role in the enzyme's active site for decarboxylating specific porphyrinogens, while arginine modification also impacted decarboxylation but didn't act as a binding site for them.
Article Abstract
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.
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| http://dx.doi.org/10.1016/0020-711x(94)90019-1 | DOI Listing |
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Porphyria-induced hepatic porphyrinogen carboxy-lyase inhibitor and its interaction with the active site(s) of the enzyme.
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Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Argentina.
Porphyrinogen carboxy-lyase is an enzyme that sequentially decarboxylates uroporphyrinogen III (8-COOH) to yield coproporphyrinogen III (4-COOH). In mammals this enzyme activity is impaired by hexachlorobenzene treatment, through generation of an enzyme inhibitor. The interaction of porphyrinogen carboxy-lyase inhibitor, extracted from the liver of hexachlorobenzene-treated rats, with substrate decarboxylation sites on the enzyme, was studied using four different carboxylated substrates belonging to the isomeric III series of naturally-formed porphyrinogens containing 8-,7-,6- and 5-COOH.
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