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Comparative oxidative rates of methionine hydroxy analogue in rat and chicken kidney.

1. L-2-HAOX A and L-2-HAOX B were purified from chicken and rat kidney with purification factors of 550 and 45, respectively. 2. It was established that both enzymes were tetrameric (M(r) = 169,000) and consisted of 40 kDa monomers. 3. While chicken kidney L-2-HAOX A is N-terminally blocked like spinach glycolate oxidase and chicken liver L-2-HAOX A, L-2-HOAX B begins with a Pro residue. 4. The kinetic parameters of L-HMB oxidation by L-2-HAOX A and B were determined. 5. The results are particularly interesting as regards L-HMB oxidation by L-2-HAOX B.

Alcohol Oxidoreductases↗
PubMed1988

Chemical and enzymic oxidation by tyrosinase of 3,4-dihydroxymandelate.

Tyrosinase usually catalyses the conversion of monophenols into o-diphenols and the oxidation of diphenols to the corresponding o-quinones. Sugumaran [(1986) Biochemistry 25, 4489-4492] has previously proposed an unusual oxidative decarboxylation of 3,4-dihydroxymandelate catalysed by tyrosinase. Our determination of the intermediates involved in the reaction demonstrated that 3,4-dihydroxybenzaldehyde is not the first intermediate appearing in the medium during the enzymic reaction. Re-examination of this new activity of tyrosinase has demonstrated that the product of the enzyme action is the o-quinone, which, owing to its instability, evolves to the final product, 3,4-dihydroxybenzaldehyde, by a chemical reaction of oxidative decarboxylation.

Ascorbic Acid↗
PubMed1976

Metabolism of DL-(+/-)-phenylalanine by Aspergillus niger.

A fungus capable of degrading DL-phenylalanine was isolated from the soil and identified as Aspergillus niger. It was found to metabolize DL-phenylalanine by a new pathway involving 4-hydroxymandelic acid. D-Amino acid oxidase and L-phenylalanine: 2-oxoglutaric acid aminotransferase initiated the degradation of D- and L-phenylalanine, respectively. Both phenylpyruvate oxidase and phenylpyruvate decarboxylase activities could be demonstrated in the cell-free system. Phenylacetate hydroxylase, which required reduced nicotinamide adenine dinucleotide phosphate, converted phenylacetic acid to 2- and 4-hydroxyphenylacetic acid. Although 4-hydroxyphenylacetate was converted to 4-hydroxymandelate, 2-hydroxyphenylacetate was not utilized until the onset of sporulation. During sporulation, it was converted rapidly into homogentisate and oxidized to ring-cleaved products. 4-Hydroxymandelate was degraded to protocatechuate via 4-hydroxybenzoylformate, 4-hydroxybenzaldehyde, and 4-hydroxybenzoate.

Aldehyde Oxidoreductases↗