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INVOLVEMENT OF ESSENTIAL LYSINE RESIDUES IN THE CATALYTIC ACTIVITY OF GLUCOSE 6-PHOSPHATE DEHYROGENASE PURIFIED FROM STREPTOMYCES AUREOFACIENS | ||
| Iranian Journal of Science | ||
| مقاله 11، دوره 31، شماره 3، اسفند 2007، صفحه 313-320 اصل مقاله (127.38 K) | ||
| نوع مقاله: Research Note | ||
| شناسه دیجیتال (DOI): 10.22099/ijsts.2007.2370 | ||
| نویسندگان | ||
| B. HAGHIGHI* ؛ F. FALAHATI | ||
| Department of Clinical Biochemistry, School of Pharmacy, Medical Sciences University of Esfahan, Esfahan, I. R. of Iran | ||
| چکیده | ||
| Glucose 6- phosphate dehydrogenase from streptomyces aureofaciens was purified and inactivated by pyridoxal 5′-phosphate (PLP). The inactivation was a pseudo-first order and time-dependent reaction. Complete inactivation was achieved at 0.2mM PLP within 16 minutes. The type of inhibition was competitive with respect to Glucose 6- phosphate. Spectral characteristics of PLP-enzyme complex corresponded to the formation of a Schiff’s base between PLP and lysine residue(s) of the enzyme. Intrinsic protein fluorescence sharply decreased upon PLP modification with about a 10 nm red shift. The presence of glucose 6-phosphate in the incubation mixture prevented the fluorescence change. Fluorescence studies revealed that NAD+ and NADP+ binding induces different conformational changes in pyridoxylated enzyme. The stochiometry of PLP binding to the enzyme showed that 2 moles of lysine residues were modified per mole of enzyme. The data indicated that the modified lysine residues are involved in substrate binding and/or catalytic activity of this enzyme. | ||
| کلیدواژهها | ||
| Glucose 6-phosphate dehydrogenase؛ pyridoxal 5’-phosphate؛ essential lysine residue | ||
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