Studies on the catalytic activity of human hepatic porphobilinogen deaminase.
Porphobilinogen deaminase was purified from human hepatocytes. A variety of group specific reagents have been used to achieve site-specific modifications to evaluate the potential role of such groups in the whole catalytic cycle. Treatment with dicarbonyl reagents caused a rapid loss in activity tha...
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| Autores principales: | , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_10399712_v42_n4_p685_Mazzetti |
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| Sumario: | Porphobilinogen deaminase was purified from human hepatocytes. A variety of group specific reagents have been used to achieve site-specific modifications to evaluate the potential role of such groups in the whole catalytic cycle. Treatment with dicarbonyl reagents caused a rapid loss in activity that was time and concentration dependent. Protection experiments revealed that arginine residues are involved in the binding of the substrate. Treatment with Woodward's reagent K showed the fastest inactivation of deaminase (85% in 30 sec at 30 mM) which was pH dependent and could be prevented by the presence of substrate, suggesting that deprotonated carboxylated groups from Asp/Glu are essential for catalytic activity. Kinetic analysis gave values of 0.3 sec-1 for the k3 rate constant and 8 x 10-2 M for the K(I) of the non covalent complex between deaminase-Woodward's Reagent K. |
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