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Biomedical subjects

J P Lambooy

Publications and source records attributed to J P Lambooy.

At least 19 recordsLinked to original sources
PubMed1985

Covalent bonding of riboflavin homologs by hepatic mitochondrial membrane enzymes.

Radioactive riboflavin and homologs of riboflavin possessing an ethyl group in positions 7- or 8-, or both were used to investigate the covalent bonding of the flavins. No strict correlation could be found between the location of the ethyl group and the activities of the enzymes known to be covalently-bound flavoproteins. It is proposed that the widely varying activities of these enzymes when utilizing certain homologs is the result of a combination of the abnormal flavin coenzyme and the differences in the specificity of the apoenzymes in the various tissues.

Animals↗
PubMed1984

Riboflavin analogs utilized for metabolism by a Lactobacillus casei mutant.

Several new halogen-containing riboflavin analogs that are antagonists for the stock strain of Lactobacillus casei have been found to be utilized by a mutant strain of the microorganism for growth and acid production. Riboflavin analogs consisting of all combinations of a single aliphatic group (methyl or ethyl) and a single halogen group (chloro or bromo) in positions 7 and 8 of the isoalloxazine nucleus possess this property. The analog devoid of substituents in positions 7 and 8 and the analog possessing a methyl group in position 7 and a cysteinyl group in position 8, were inert for both strains of the microorganism.

Acids↗
PubMed1982

Utilization of analogues of riboflavin for growth and survival of the chicken.

Groups of normal 5-day-old chicks of the Single Comb White Leghorn strain were fed diets containing no riboflavin, riboflavin, or one of several analogues of riboflavin, to explore differences between the classes Mammalia and Aves. It was found that 7-ethyl-8-methyl-flavin was a suitable replacement for the vitamin. 7-Methyl-8-ethyl-flavin permitted early growth of the chicks, but it did not allow survival when fed in place of riboflavin. The inability to utilize 7-methyl-8-ethyl-flavin represents a real difference in the utilization of flavin between the classes Mammalia and Aves. Other flavin analogues supported some growth, but the chicks did not survive. All groups showed better growth responses than was shown by the riboflavin-deficient group.

Animals↗
PubMed1981

Brain monoamine oxidase and replacement of its coenzyme flavin in rats.

The influence of 7-ethyl-8-methylflavin and 7-methyl-8-ethylflavin, vitamin-like homologues of riboflavin, on rat brain mitochondrial monoamine oxidase (MAO) was studied using tyramine as substrate. While riboflavin deficiency caused the enzyme activity to fall to 80% of norma, when 7-ethyl-8-methylflavin replaced riboflavin as the precursor of its coenzyme, it caused essentially complete loss of the enzyme activity. We showed that while 7-ethyl-8-methylflavin can serve as a coenzyme for MAO, 7-methyl-8-ethylflavin cannot serve as coenzyme for this enzyme.

Animals↗
PubMed1977

Utilization of analogues of riboflavin by the riboflavin-deficient chick embryo.

Detailed studies of the biological activity of several analogues of riboflavin in the riboflavin-deficient chick embryo were undertaken to extend our knowledge of the comparative biochemistry of these flavins. The riboflavin-deficient eggs were produced by hens homozygous for an autosomal recessive gene (rdrd). 7-Ethyl-8-methyl-flavin was found to be an adequate replacement for riboflavin in che chick embryo, a finding which mimics its effect in the riboflavin-deficient rat. 7,8-Diethyl-flavin was found to be an antagonist in the chick embryo as had been found to be true in the rat. 7-Methyl-8-ethyl-flavin can not be used as a replacement for riboflavin in the chick embryo and further, it inhibits the utilization of riboflavin in normal eggs. 7-Methyl-8-ethyl-flavin had been found to be an adequate replacement for riboflavin in the riboflavin-deficient rat. The classes mammalia and aves are clearly different in respect to the utilization of this flavin.

Animals↗
PubMed1977

Utilization of riboflavin homologues by D-amino acid oxidase and xanthine oxidase.

D-Amino acid oxidase and xanthine oxidase, two enzymes possessing ionically bound flavin coenzymes have been studied with their flavin coenzymes derived from either 7-ethyl-8-methyl-flavin or 7-methyl-8-ethyl-flavin, vitamin-like homologues of riboflavin. 7-Ethyl-8-methyl-flavin caused a significant reduction of both D-amino acid oxidase and xanthine oxidase in the liver, but not in the kidney. 7-Methyl-8-ethyl-flavin caused a significant reduction of D-amino acid oxidase in both the liver and kidney, a significant reduction of xanthine oxidase in the liver, but a large and significant increase of the latter enzyme in the kidney. An improved procedure for the assay of xanthine oxidase has been described.

Animals↗