Studies on the metabolism of o-aminophenol purification and properties of isophenoxazine synthase from Bauhenia monandra

An enzyme which catalyzes the oxidative conversion of o-aminophenol to 2-amino-3-H-isophenoxazin-3-one has been purified 396-fold by using standard fractionation procedures. The enzyme is specific for o-aminophenol and has pH and temperature optima at 6.2 and 40 °, respectively. It is insensitive to metal chelating agents but is inhibited by several reducing substances. There is no cofactor or metal ion requirement for the reaction. A competitive type of inhibition was observed with structural analogs such as anthranilic acid and 3-hydroxyanthranilic acid. There are no free sulfhydryl groups in the enzyme, but preincubation of the enzyme with substrate or substrate analogs resulted in the liberation of titratable free sulfhydryl groups. The mechanism of biosynthesis of isophenoxazine ring is discussed.

Isolation and properties of catechol-cleaving yeasts from coir rets

A suitable method for the selective isolation of catechol-cleaving yeasts from coir rets has been worked out. The yeast strains, all belonging toDebaryomyces hansenii, were found to demand biotin as an essential vitamin. The organism has the ability to grow on catechol, phenol and some related compounds as sole source of carbon. It tolerates 0.4% catechol and 0.26% phenol. Evidence was obtained that the catechol-cleaving enzyme of the isolates is a pyrocatechase. Some properties of the cell-free catechol oxygenase are described.

Spectroscopic studies of the donor properties of triphenyl-amine, -phosphine, -arsine and -stibine interaction with iodine and phenol

The interaction of iodine with triphenylamine ,tripheny lphosphine, triphenylarsine and triphenystibine has been investigated by electronic spectroscopy. Transformation of the outer charge-transfer complexes to the inner complexes (quarternary salts) has been examined. The relations of the ionization potentials of the donors with the hvc.t have been discussed and various c.t. parameters have been estimated. Hydrogen bonding of these donors with phenol have been reported.

Purification and properties of an inhibitor for nicotinamide-adenine dinucleotidase from Mycobacterium tuberculosis H37Rv

The excess of free inhibitor for the enzyme NADase present in the crude cell-free extracts of Mycobacterium tuberculosis H37Rv has been purified by chromatography on a DEAE-cellulose column and adsorption and elution from alumina Cγ-gel. Some of the properties of the purified inhibitor have been studied and attempts have been made to elucidate the nature of combination between the enzyme and the inhibitor. The purified inhibitor may be glycoprotein in nature, and considerable loss in the activity of the inhibitor preparations could be brought about by trypsin digestion. The inhibitor was specific for the enzymes from M. tuberculosis H37Rv or H37Ra and could be stored for at least 6 months in the frozen state below 0 ° without any significant loss in activity. The inhibition was noncompetitive with respect to the substrates, and the enzyme-inhibitor complex formed was undissociable.