Effect of retinol on the hemolysis and lipid peroxidation in vitamin Ε deficiency.

A study on the effect of retinol in vitro on the hemolysis of vitamin Ε deficient rat red blood cells showed that retinol enhanced the lysis of the Ε deficient cells as compared to the lysis of normal cells. The lipid peroxidation present during hydrogen peroxide induced lysis of Ε deficient cells was however markedly inhibited in the presence of retinol without affecting the rate of lysis. In an actively peroxidising system of non-enzymatic lipid peroxidation of rat liver or brain homogenates and of brain lysosomes incubated with human erythrocytes, no lysis was obtained; incorporation of retinol in such systems resulted in lysis but no peroxidation. Hydrogen peroxide generating substances almost completely inhibited the lysis of normal human erythrocytes by retinol, but linoleic acid hydroperoxide and auto-oxidised liver or brain homogenates and ox-brain liposomes increased the lysis. It is concluded that vitamin Ε deficient erythrocyte hemolysis may be augmented by retinol, an anti-oxidant, having a lytic function without the peroxidation of stromal lipids.

Fructose diphosphate aldolase-Class I (Schiff base) from Mycobacterium tuberculosis H37Rv.

An aldolase was partially purified from fermenter grown Mycobacterium tuberculosis H37Rv cells. The aldolase has a molecular weight of 150,000, possesses a tetrameric structure and cleaves both fructose diphosphate and fructose- 1-phosphate, the former being cleaved 17 times faster. The enzyme was inactivated by treatment with NaBH4 in the presence of fructose diphosphate or dihydroxyacetone, phosphate suggesting Schiff base formation during its catalytic function. Thiol reagents, EDTA and metal ions had no apparent effect on the aldolase activity. These results show that aldolase is of Class I type. However, this enzyme, unlike the mammalian Class I aldolase, was unaffected by carboxypeptidase A. Nethylmaleiniide and dithionitrobenzoic acid.

Studies on hemolysis of human erythrocytes by linoleic acid.

The results presented in this paper show that lysis of human erythrocytes by linoleic acid is not caused by peroxidation of the fatty acid. Peroxidase, superoxide dismutase and scavengers of Ο · and OH had no effect on the lysis while catalase showed only marginal inhibition suggesting that Ο , OH , O and H2O2 do not play any direct role in hemolysis by linoleic acid. Generators of H2O2 inhibited the lysis completely and methemoglobin cells were more resistant to hemolysis by linoleic acid. The fatty acid did neither bind to nor fomed complex with red cell ghosts. Membrane oxidation of sulphydryl groups was also not involved in the lysis. β-Carotene, retinol and bile salts enhanced the lysis, while, cholesterol but not cholesterol acetate, inhibited it. Taurocholate-pretreated cells were more susceptible to linoleic acid lysis. These observations suggested-that lysis by linoleic acid may be due to its detergent property.

Alpha-tocopheryl acetate hydrolase in chicken liver. Characterisation and properties.

An enzyme catalysing the hydrolysis of a-tocopheryl acetate was characterised in chicken liver. The enzyme was localised in the microsomes, had an optimum pH 8·6 and a Km value of 0·5 mM. The enzyme did not hydrolyse retinyl acetate, cholesteryl acetate and ethyl acetate, thus indicating a high degree of specificity. a-Tocopheryl acetate hydrolase required bile salts as a specific cofactor. The results suggested a role for this enzyme in the absorption of vitamin E.