Glutathione S-Transferase Isoforms in the Seminiferous Tubular Fluid, Tissue Distribution and Sex Steroid Binding by Rat GST Mi

Abstract

A comparative study was made regarding the stability and catalytic activity of two related enzymes (Alcohol dehydrogenase from Tbermoanaerobacter brockii TBADH and the mesophilic enzyme from Yeast YADH)in the medium of various organic solvents of different degrees of hydrophobicity. It was clearly found that both enzymes remains stable at high temperatures after prolonged incubation in hydrophobic solvents than in thier hydrophilic counterparts. However, in the presence of pyridine the catalytic activity of TBADH reduced considerably at high temperatures whereas YADH is inactivated completly even at room temperature. The effect of water-miscible solvents on the activity of both enzymes have also been investigated. Interestingly, the thermophilic enzyme was more active at high concentrations of dioxane, but low amount of dimethylformamide (DMF) inhibit its catalytic activity, while these solvents exert adverse effect on mesophilic counterpart. These observations indicate that (i) TBADH is more resistant than YADH toward extreme organic meliue as well as high temperatures and (ii) it is possible to provide thermophilic characteristics to a mesophilic enzyme by using a proper microenvironment.The semineferous tubular fluid (STF) provides the microenvironment necessary for spermatogenesis primarily through the secretions of the seminiferous tubule (ST). Previous studies from this laboratory have shown the presence of GSTs in adult rats. In the present study we have shown the isoform composition, testicular source and possible function of rat GST. The major GST isoforms present in rat STF-GST share extensive N terminal similarity with rat GST-MI, M2, M3 and Alpha subunits. Molecular mass of the individual peaks have been done both in STF-GST and GST from liver. Rat STF GST M1 was higher by 325 Da.Peptide digest analysis data of the selected peaks were done from liver and STF revealed considerable simi1arity.The above studies showed consideraable stuctural similarity between liver and STF-GST. Further studies with radiolabelled GST showed that Seroli cells were the prime secretors of GST.Functionally, STF GSTs have the ability to bind to oestradiol and testosterone, two important hormones in the ST that are essential for spermatogenesis. Rat GST-MI carries out this function. 01Hyperthemostable AONS: the first committed enzyme in E. coli biotin biosynthesis has a tropical relative An essential cofactor for fatty acid metabolism in all organisms, biotin is produced in small quantities only in bacteria, fungi and plants. The catalyst for the first committed step of this process in E.coli, 8-amino-7-oxononanoate synthase ( A O N S EC 2.3.1.47), is the product of the bioF gene and catalyses the decarboxylative condensation reaction between L-alanine and Pimeloyl CoA to produce 8-amino-7-oxononanoate. The structure of this protein (1) confirms that AONS functions as a homodimer, each monomer of which has a mass of 41.7 kDa and is composed of three distinct domains. The active site is found in a deep cleft within the central,...