The induction of rat liver L-threonine deaminase by nicotinamide.
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Animals↗
Biomedical subjects
E Marinello
Publications and source records attributed to E Marinello.
The delayed activation of liver xanthine oxidase in rats treated with nicotinamide.
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Animals↗
Synthesis and NMR properties of 2-(4-pyridyl) thiazolidine-4-carboxylic acids.
Various thiazolidine derivatives, obtained through condensation between pyridoxal or pyridoxal-5'-phosphate with several aminothiols, have been obtained and examined for their NMR spectra. For the compounds tested, we demonstrated the presence in solution of the two diasteroisomeric thiazolidines, A and C, which differ for the configuration at C2, and are interconverted via the open chain Schiff's base, with different rates, depending on the pH. The possibility that, when aminothiols react with PLP bound to the enzyme, only one of the two diasteroisomers may be formed, and the biological role of such derivatives is discussed.
Cysteine↗
Spinach threonine dehydratase. Inhibition by L-cysteine and D-cysteine.
L-threonine deaminase from spinach is inhibited by D- and L-cysteine. The inhibition patterns by D-cysteine and by L-cysteine are non-competitive. The value of Ki for D-cysteine and L-cysteine is of the same order of magnitude. Inhibitions by L-isoleucine and L-cysteine are additional. These results indicate that inhibition by L-cysteine occurs on a site of enzyme which is different from the binding site for L-isoleucine and L-valine. Probably L-cysteine and D-cysteine form the thiazolidinic ring with a PLP mole. Which is not costituent of the active site, but located in a different region.
Binding Sites↗
Purification and properties of rat liver L-threonine deaminase.
Rat liver threonine deaminase has been partially purified. The enzyme deaminates L-threonine and L-serine, is not affected by isoleucine, nor by AMP and ADP. L-cysteine and analogues are inhibitors of threonine deaminase and it is very likely that the inhibition is due to the formation of a thiazolidine ring with PLP bound to the enzyme. However, the simple formation of this ring does seem to explain completely the different degree and type of inhibition shown by L-cysteine and analogues. The hypothesis that the different behaviour of L- and D-cysteine is due also to interactions independent of the formation of thiazolidinic ring is discussed.
Animals↗
[Myelin].
The lipid and protein composition and the metabolic turnover of myelin in the C.N.S., are briefly reported. For a better understanding, it seemed useful to introduce some historical data on the discovery of myelin and to give a morphological description at structural and ultrastructural level.
Animals↗