Glucosamine-6-phosphate deaminase activity during connective tissue growth

Incorporation of sulphate by chick-embryo corium. Nature and products of the process in vitro

1. The incorporation of sulphate into the trichloroacetic acid-precipitable fraction of 9-day chick-embryo corium, incubated in Krebs-Ringer phosphate buffer, pH7, is dependent on the sulphate concentration of the medium. Uptake of sulphate is linear with time for 3.5-4hr. and is maximal at 37.5 degrees in the presence of air or oxygen. d-Glucose stimulates the incorporation of sulphate but l-glutamine has no effect. 2. Incorporation of sulphate by the chick corium is enzymic and apparently involves the synthesis of active sulphate (adenosine 3'-phosphate 5'-sulphatophosphate) and the transfer of sulphate from adenosine 3'-phosphate 5'-sulphatophosphate to acceptor glycosaminoglycuronoglycan. This proposal on the nature of the process is suggested by the similarity between the energy of activation calculated for sulphate-incorporation in the chick-corium preparation and the energy requirement reported for sulphate-activation with purified yeast enzymes. 3. The 9-day chick-embryo corium is composed principally of fibroblasts; there are no histologically demonstrable mast cells. The young fibroblast is apparently responsible for the incorporation of sulphate into glycosaminoglycuronoglycans tentatively identified as chondroitin sulphate(s), heparan sulphate and heparin-like material.

[Metabolism of glucosamine in the liver of Scyliorhinus canicula (selachian)]

(1) The metabolism of the glucosamine was studied in the liver of S. canicula, after injection of D-(1-14C) glucosamine into the animal. (2) The labelled acid-soluble derivatives were separated by ion exchange columns and characterized by chromatography and electrophoresis, and were identified as glucosamine, glucosamine 6-P, N-acetylglucosamine, N-acetylmannosamine, N-acetylneuraminic acid, N-acetylglucosamine 6-P, N-acetylglucosamine 1-P, N-acetylmannosamine 6-P, UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine. (3) The variation with time after glucosamine injection of the radioactivity of the fractions separated on Dowex 1-X4 was investigated. This study showed a decrease of the radioactivity in the fraction 1 (glucosamine and glucosamine 6-P), an increase in the fraction II (N-acetylneuraminic acid) and the fraction IV (UDP-N-acetylhexosamines), and a stability in the fraction III (phosphorylated N-acetylhexosamines). (4) The absence of label in neutral hexoses and their phosphorylated derivatives was interpretated as due to the weak activity of the glucosamine 6-P isomerase, which is positively modulated by the N-acetylglucosamine 6-P.

The metabolism of mucopolysaccharides. 3. The effect of adrenocortical hormones on enzymes involved in glucuronide synthesis and metabolism in connective tissue

The levels of activity of hexokinase, phosphoglucomutase, uridine diphosphoglucose pyrophosphorylase, and uridine diphosphoglucose dehydrogenase, which are involved in the synthesis of glucuronic acid, and the levels of glucuronosyltransferase and β-glucuronidase, which are involved in its metabolism, were studied in connective tissue from polyvinyl sponge implants from sham-operated and adrenalectomized rats which had received "replacement therapy" of individual steroids.The levels of activity of these enzymes were significantly increased in sham-operated rats which had been treated with corticosterone, cortisone, or hydrocortisone. In adrenalectomized animals, the increased or decreased enzyme activities were restored to normal levels by "therapy" with corticosterone, cortisone, or hydrocortisone. In some cases there was an over-correction at the particular level of hormone treatment. In both sham-operated and adrenalectomized animals, treatment with deoxycorticosterone, progesterone, or Reichstein's substance S frequently, but not always, resulted in little or no change in activity of the enzymes.