Comparison between crab hepatopancreas and rat liver uroporphyrinogen decarboxylase

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology Vol. 133; no. 2; pp. 251 - 256
• Main Authors: Chaufan, G., Corvi, M., Armesto, A., San Martı́n de Viale, L.C., Luquet, C., Rı́os de Molina, M.C.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-10-2002
• Subjects: Activation energy; Animals; Crab hepatopancreas; Decapoda (Crustacea) - enzymology; Decarboxylation; Digestive System - enzymology; Environmental Pollutants - metabolism; Enzymatic properties; Haem; Hydrocarbons, Halogenated - metabolism; Hydrogen-Ion Concentration; Kinetic parameters; Kinetics; Liver - enzymology; Optimum pH; Optimum temperature; Porphyrinogens - metabolism; Porphyrins; Rat liver; Rats; Rats, Wistar; Temperature; Uroporphyrinogen decarboxylase; Uroporphyrinogen Decarboxylase - chemistry; Uroporphyrinogen Decarboxylase - metabolism; Haem; Kinetic parameters; Rat liver; Enzymatic properties; Crab hepatopancreas; Optimum temperature; Activation energy; Optimum pH; Porphyrins; Uroporphyrinogen decarboxylase
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/S1096-4959(02)00151-3

We characterized Uroporphyrinogen decarboxylase (UroD) (E.C. 4.1.1.37) in hepatopancreas of the crab
Chasmagnathus granulatus as a first step to establish this enzyme as a possible biomarker for environmental contamination. We performed a comparative study of crab UroD with the enzyme UroD present in Wistar rat liver, which is known as a useful indicator of intoxication by polyhalogenated aromatic hydrocarbons (PAHs). The final products were the same in crab and rat UroD: the remaining substrate (8-carboxyl-porphyrinogen), the final product Coproporphyrinogen (4-COOH) and intermediate compounds with 7-, 6- and 5-COOH. The elimination of the second carboxyl group seems to be the rate-limiting step in this multiple decarboxylation, because large amounts of 7-COOH porphyrinogen are accumulated. The
V
max/
K
m ratio was 100-fold higher for rat liver UroD than for crab hepatopancreas UroD, suggesting a higher efficiency of the rat enzyme. Optimum pH for enzyme activity was 7.2 and 6.8 for crab and rat, respectively. Although both systems showed the same optimum temperature (47 °C), the activation energy was clearly different, 51.5 kJ/mol for
C. granulatus and 5.4 kJ/mol for
Rattus norvegicus (Wistar strain). Superdex 75 gel chromatography yielded a single symmetrical peak with an apparent molecular mass of 48±3 kDa for crab hepatopancreas UroD, suggesting the existence of only one enzymatic species in
C. granulatus.