Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.1.1.37 (malate dehydrogenase)
 4,591 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibition of pig heart mitochondrial malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37) by the thyroxine and structurally related compounds was studied to resolve a longstanding question about the exact nature of the inhibition. Thyroxine, in freshly prepared solution, was found to be a "pure" competitive inhibitor relative to the nucleotide cofactor. Upon standing in diffuse daylight, solutions of thyroxine showed increased ability to inhibit the enzyme, presumably as a result of oxidation of enzyme sulfhydryl groups by free iodine that is released photochemically. This behavior probably accounts for earlier reports of irreversible inactivation by thyroxine. Comment is made on the implications of these findings to the mechanism of thyroid hormmone action.
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PMID:Inhibition of malate dehydrogenase by thyroxine and structurally related compounds. 20 20

Experimental hyperthyroidism induced in rats by daily injections of 3,3',5,5'-tetraiode-L-thyroxine (0.5 mg/kg i.p.) for 14 days resulted in a significant increase in heart weight and heart weight/body weight ratio. Hemodynamic and morphological studies were performed in one group. Thyroxine-treated rats showed a characteristic cardiovascular hyperdynamic state, such as tachycardia and augmented rate of contraction, but no evidence of heart failure such as elevated end-diastolic pressures. The cardiac cells in hyperthyroid rats had a significantly larger diameter and more mitochondria than did those of the control rats. In another group the activities of cardiac enzymes involved in energy utilization and liberation were measured biochemically and compared with those of normal controls. Hyperthyroidism resulted in increased specific activity of cytochrome C oxidase and actomyosin ATPase in the myocardium. The specific activity of long-chain acyl-CoA synthetase, carnitine palmityl-transferase, carnitine acetyltransferase, malate dehydrogenase and citrate synthase showed a moderate to marked increment, whereas the specific activity of lactate dehydrogenase and pyruvate kinase remained at the control values. These results suggest that in hyperthyroid rat hearts the functions of both energy liberation and utilization systems are enhanced to meet the added workload. Moreover, the increased activity of the enzymes participating in fatty acid metabolism suggest that in thyroxine-induced hypertrophic and hyperdynamic rat hearts, fatty acids contribute more to the energy supply than do carbohydrates.
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PMID:Biochemical and morphological study of cardiac hypertrophy. Effects of thyroxine on enzyme activities in the rat myocardium. 315 81

The effect of thyroxine on the specific activities of testicular enzymes of the pyruvate/malate cycle involved in lipogenesis were studied in prepubertal, pubertal and adult rats. Thyroxine (25 micrograms/100 g body weight) treatment for 1 month increased the specific activity of isocitrate dehydrogenase (NADP+) but the specific activities of ATP-citrate lyase, malate dehydrogenase and malic enzyme were inhibited. Withdrawal of thyroxine treatment from hyperthyroid rats brought back all enzyme activities to normal. The study reveals a direct, specific influence of thyroxine on different testicular enzymes of the pyruvate/malate cycle.
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PMID:Effect of thyroxine-induced hyperthyroidism on some testicular enzymes of the pyruvate/malate cycle. 669 44

The specific activities of testicular enzymes of the pyruvate/malate cycle involved in lipogenesis after thyroidectomy and thyroxine replacement were studied in prepubertal, pubertal and adult rats. Thyroidectomy induced testicular ATP citrate-lyase, malate dehydrogenase and malic enzyme activities and inhibited isocitrate dehydrogenase (NADP+) activity. Thyroxine treatment on thyroidectomized animals reverted all enzyme activities to normal. The result suggests that thyroid hormones have a differential effect on testicular enzymes of the pyruvate/malate cycle involved in lipogenesis.
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PMID:Effect of thyroidectomy on testicular enzymes of the pyruvate/malate cycle involved in lipogenesis. 682 30