The primary functional role of collagen is as a supporting tissue and it is now established that the aggregated forms of the collagen monomers are stabilised to provide mechanical strength by a series of intermolecular cross-links. In order to understand the mechanical properties of collagen, it is necessary to identify and quantitatively determine the concentration of the cross-links during th...

3-Mercaptopyruvate, generally believed to be formed by enzymatic transamination of L-cysteine and by the oxidative deamination of L-cysteine, has been found to exist in solution, in equilibrium with the cyclic dimer, 2,5-dihydroxy-1,4-dithiane-2,5-dicarboxylic acid; the equilibrium markedly favors the cyclic dimer in aqueous solution at pH 5-7. However, in neutral solutions, and especially in a...

Whether oxidative deamination is the favored initial step in the catabolism of histidine, as may be the case with many of the amino acids, is open to question. The supporting evidence of Krebs (1) is less striking with r,-histidine than with most other natural amino acids. Kidney slices yielded somewhat more ammonia in the presence of histidine and oxygen than in the absence of either, and live...

Armstrong & McMillan (1957) identified 4hydroxy-3-methoxymandelic acid (vanilmandelic acid) in normal human urine and demonstrated that increased quantities were excreted after noradrenaline infusion and by patients with the catecholamine-secreting tumour, phaeochromocytoma. Subsequent work has established that 3methoxylation followed by oxidative deamination to 4-hydroxy-3-methoxymandelic acid...

The original identification of indole-3-acetic acid as a growth factor for plants was made by Kogl et al. (1) on material isolated from human urine. The presence of IA’ in human urine has been amply verified by many investigators. Previous measurements of this substance in urine were determined by plant-growth bioassay or paper chromatography, no satisfactory chemical method being available. To...

In recent years the metabolic fate of the individual carbon atoms of the aromatic amino acids has been rather completely elucidated, largely by the use of isotopic labeling techniques (l-3). Very little is known, however, concerning the enzymatic mechanisms whereby the complicated transformation of phenylalanine and tyrosine to acetoacetate is effected. A recent contribution in this direction w...