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Serine hydroxymethyltransferase from mammalian and bacterial sources is a pyridoxal-5'-phosphate-containing enzyme, but the requirement of pyridoxal-5'-phosphate for the activity of the enzyme from plant sources is not clear. The specific activity of senne hydroxymethyltransferase isolated from mung bean (Vigna radiata) seedlings in the presence and absence of pyridoxal-5'-phosphate was comparable at every step of the purification procedure. The mung bean enzyme did not show the characteristic visible absorbance spectrum of a pyridoxal-5'-phosphate protein. Unlike the enzymes from sheep, monkey, and human liver, which were converted to the apoenzyme upon treatment with L-cysteine and dialysis, the mung bean enzyme similarly treated was fully active. Additional evidence in support of the suggestion that pyridoxal-5'-phosphate may not be required for the mung bean enzyme was the observation that pencillamine, a well-known inhibitor of pyridoxal-5'-phosphate enzymes, did not perturb the enzyme spectrum or inhibit the activity of mung bean serine hydroxymethyltransferase. The sheep liver enzyme upon interaction with O-amino-D-serine gave a fluorescence spectrum with an emission maximum at 455 nm when excited at 360 nm. A 100-fold higher concentration of mung bean enzyme-O-amino-Dseine complex did not yield a fluorescence spectrum. The following observations suggest that pyridoxal-5'-phosphate normally present as a coenzyme in serine hydroxymethyltransferase was probably replaced in mung bean seine hydroxymethyltransferase by a covalently bound carbonyl group: (a) inhibition by phenylhydrazine and hydroxylamine, which could not be reversed by dialysis and or addition of pyndoxal-5'phosphate; (b) irreversible inactivation by sodium borohydride; (c) a spectrum characteristic of a phenylhydrazone upon interaction with phenylhydrazine; and (d) the covalent labeling of the enzyme with substrate/product serine and glycine upon reduction with sodium borohydride. These results indicate that in mung bean seine hydroxymethyltransferase, a covalently bound carbonyl group has probably replaced the pyridoxal-5'-phosphate that is present in the mammalian and bacterial enzymes.

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The aim of this study is to investigate the antioxidant defense system induced by the methanol extract of Bauhinia racemosa L.(MEBR) against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in Wister albino rats. The effects of MEBR on surface visible macroscopic (Morphometry) liver lesions (neoplastic nodules) and the levels of serum enzymes, lipid peroxidation and antioxidants were evaluated in NDEA-induced hepatocarcinogenesis in rats. In rats treated, with NDEA, significantly elevated levels of serum enzymes (SGOT, SGPT and ALP), bilirubin and decreased levels of protein and uric acid were observed. Significantly elevated amount of malondialdehyde (MDA), the end product of lipidperoxidation, indicated higher levels of lipid peroxidation, which was accompanied by significantly decreased levels of antioxidants like vitamin C, vitamin E, reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT). Administration of MEBR was able to suppress nodule development/hepatocellular lesion formation in rats. The extract treatment increases in antioxidant levels and dramatic decreases in lipid peroxidation levels. MEBR also produced a protective effect by decreasing the level of serum enzymes, bilirubin and increased the protein and uric acid levels. The results suggest that MEBR exert chemopreventive effects by suppressing nodule development and decreasing lipid peroxidation and enhancing the levels of antioxidants in NDEA carcinogenesis by reducing the formation of free radicals.

Articles you may be interested inMolecular structure and nuclear quadrupole coupling tensors of 1 4N and 3 5Cl in 1chloro2,4 dinitrobenzene. Phase I J. Chem. Phys. 90, 483 (1989); 10.1063/1.456499 Zeeman Effect Study of the Nuclear Quadrupole Resonance of 81Br in 4,4′Dibromodiphenylether and 4,4′Dibromodiphenylthioether J.The Zeeman effect of NQR was studied in l-chloro-2,4-dinitrobenzene. A low value of the asymmetry parameter (0.10) was obtained. Four physically inequivalent field gradients were located and their orientations in the crystallographic abc system were determined using symmetry considerations. From these data the orientations of the molecules in the unit cell were determined. The results agree well with the two-dimensional x-ray structural data. The bond characters of the C-Cl bond were calculated, and the values compare well with those generally obtained for C-Cl bonds in chlorine derivatives of benzene.