Transglutaminase activity in normal and hereditary cataractous rat lens and its partial purification.

Hereditary cataractous rat lenses showed significantly higher specific activity for transglutaminase than the normal lenses of comparable age. Transglutaminase activity of normal lenses was distributed predominantly in the buffer-soluble fraction. The buffer-insoluble fraction showed 14% of total activity. The cortical and nuclear fractions of the normal lens showed 43% and 57% distribution of total activity, respectively. Protein solubilizing agents enhanced the activity of the enzyme in the lens homogenate in the following order: Triton X-100 greater than Tween 20 greater than Sodium dodecyl sulfate greater than Sodium deoxycholate greater than Sodium cholate greater than NaSCN greater than KI. Transglutaminase was purified 15 fold by hydrophobic affinity chromatography employing omega-amine octylagarose matrix. The purified enzyme was activated by calcium and inactivated by iodoacetamide and upon freeze-drying. Lens crystallins served as exogenous substrate for transglutaminase, with gamma-crystallin as the most effective amine acceptor.

Biochemical adaptation of rat liver in response to marginal oxygen toxicity.

1. Hepatic glucose 6-phosphate dehydrogenase activity was increased in rats exposed to 5lb/in(2) (equivalent to 27000ft), 100% O(2) when compared with control animals in a 14.7lb/in(2) (sea level), air environment. Glyceraldehyde 3-phosphate dehydrogenase, isocitrate dehydrogenase, and succinate dehydrogenase were not affected by the 5lb/in(2), 100% O(2) environment. 2. Animals exposed to the hyperoxic environment consumed food, expired CO(2) and gained weight at the same rate as normoxic control animals. Additionally, blood glucose and liver glycogen concentrations were unchanged in the hyperoxic animals. The only readily apparent physiological difference in the hyperoxic animals was a decreased haematocrit. 3. The increase in glucose 6-phosphate dehydrogenase was eliminated by the injection of actinomycin D or cycloheximide. 4. Expiration of (14)CO(2) from [1-(14)C]glucose was approximately the same in hyperoxic and normoxic rats. However, (14)CO(2) expiration from [6-(14)C]glucose was markedly decreased in the animals exposed to the hyperoxic environment. 5. Calculations of the relative importance of the pentose phosphate pathway versus the tricarboxylic acid cycle plus glycolysis indicated that the livers from animals in the 5lb/in(2), 100% O(2) environment metabolized twice as much carbohydrate by way of the pentose phosphate pathway as did those from the sea-level air control animals. 6. In livers of rats exposed to 5lb/in(2), 100% O(2) the concentrations of pyruvate, citrate and 2-oxoglutarate were increased, that of isocitrate was slightly elevated, whereas the concentrations of succinate, fumarate and malate were decreased. 7. An inactivation of both tricarboxylic acid cycle lipoate-containing dehydrogenases, pyruvate and 2-oxoglutarate, under hyperoxic conditions is proposed. 8. The adaptive significance of the induction of glucose 6-phosphate dehydrogenase and the resultant production of NADPH under hyperoxic conditions is discussed.