Suren Aghajanian

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The final two enzymes in the CoA biosynthetic pathway, phosphopantetheine adenylyltransferase (PPAT; EC and dephospho-CoA kinase (DPCK; EC, are separate proteins in prokaryotes, but exist as a bifunctional enzyme in pig liver. In the present study we have obtained sequence information from purified pig-liver enzyme, and identified the(More)
The structural flexibility and thermostability of glutamate dehydrogenase (GDH) from Clostridium symbiosum were examined by limited proteolysis using three proteinases with different specificities, trypsin, chymotrypsin, and endoproteinase Glu-C. Clostridial GDH resisted proteolysis by any of these enzymes at 25 degrees C. Above 30 degrees C, however, GDH(More)
Urea-induced effects in clostridial glutamate dehydrogenase (GDH, EC were studied by spectrophotometry, circular dichroism, FPLC, affinity chromatography and PAGE. Denaturation of enzyme occurred over a narrow range of urea concentrations (2.5-3.5 M), accompanied by inactivation of enzyme with a similar rate constant. The contribution of(More)
Hybrids of different forms of clostridial glutamate dehydrogenase (GDH) have been constructed in order to probe the basis of allosteric interaction in this hexameric enzyme. It was shown that the C320S mutant, which is fully active and shows allosteric behaviour similar to that of the wild-type enzyme, can also be renatured after unfolding in urea. Mixtures(More)
In a study of the re-activation of urea-denatured clostridial glutamate dehydrogenase (GDH) the maximum re-activation achieved without any added ligands was about 6%, but with NAD+ and 2-oxoglutarate in combination about 70%. NAD+ alone was also effective but 2-oxoglutarate was not, in striking contrast with the opposite pattern for protection of this(More)
NAD+ facilitates high-yield reactivation of clostridial glutamate dehydrogenase (GDH) after unfolding in urea. The specificity of this effect has been explored by using analogues and fragments of NAD+. The adenine portion, unlike the nicotinamide portion, is important for reactivation. Alteration in the nicotinamide portion, in acetylpyridine adenine(More)
(ADP-rib0se)polymerase (EC is a chromatin bound enzyme which performs the post-translational modification of histones and nuclear enzymes, and participates in the regulation of cellular activity [ 13. There are convincing data supporting the participation of this enzyme in cell proliferation [2]. The neoplastic transformation of tissues is(More)
In vitro subunit hybridisation is a usehl technique for exploring inter-subunit interactions in oligomeric enzymes [I]. In order to explore the basis of allosteric bebaviour in glutamate dehydrogenase from Clmtridiurn syrnbimurn, hybrid hexamers of mutants, VIZ. triple mutant, K89L/A163G/S380A [2] and C320S [3] have been constructed. The mutant C320S is hUy(More)