Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.11 (CD10)
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Ornithine transcarbamoylase (OTC) is inactivated by liver lysosomes. Carbamoyl phosphate prevents the inactivation of OTC by lysosomes, while ATP, ADP, GTP, GDP 1,N6-ethenoadenosine 5'-triphosphate and particularly epsilon-ATP stimulate it. Both stimulation and protection occur at concentrations within the physiological range of ATP and carbamoyl phosphate. Inactivation of OTC is followed by extensive proteolysis. Since the inactivation is prevented by leupeptin, antipain and L-(tosylamido-2-phenyl)ethylchloromethyl ketone, the proteolytic susceptibility of OTC to lysosomes could be due to thiol endopeptidase(s). 1,N6-Ethenoadenosine 5'-triphosphate also markedly increases OTC susceptibility to trypsin and elastase. ATP analogs had no stimulatory effect on OTC inactivation by lysosomes; none of the inhibitors of ATPases tested inhibited the ATP effect. The ATP stimulation does not require Mg2+. These findings indicate a new role for ATP, GTP and related nucleotides in protein breakdown. The ATP, ADP, GTP, GDP stimulation, together with the carbamoyl protection of OTC, agree well with the molecular plasticity hypothesis model.
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PMID:Purine nucleotides stimulate while carbamoyl phosphate protects inactivation of ornithine transcarbamoylase by disrupted lysosomes. 399 99

The spermatophore of the silkmoth,Bombyx mori, is a reactor with a specific energy-yielding system for sperm maturation, the arginine degradation cascade. On mating, the highly viscous secretions from various glands in the male reproductive tract, which contain many enzymes and their substrates, are transferred to the female bursa (b.) copulatrix to form the spermatophore. In the spermatophore, transferred arginine-rich proteins are digested by initiatorin, an Arg-C endopeptidase of serine-protease type, and a carboxypeptidase. The produced free arginine is then hydrolyzed to urea and ornithine by arginase. Ornithine is metabolized to glutamate, follwed by forming alanine and 2-oxoglutarate. The latter, as a member of TCA-cycle, is a preferred respiratory substrate for spermatozoa and accelerates the post-testicular sperm maturation.In contrast toBombyx mori, Drosophila melanogaster produces only eupyrene spermatozoa and does not form the spermatophore. The sperm of this dipteran insect acquire motility in the v. seminalis of males. As reported forDrosophila, a high glutamate-pyruvate aminotransferase activity was found in the spermatophore as well as the v. seminalis of the silkmoth. The value in the latter organ reaches 58.3% of the whole male reproductive tract that participates in transfer of the seminal fluid.In the male reproductive system ofDrosophila, the concentration of arginine is low, whereas those of urea and ammonia are high. The accessory gland secretion contains much phosphoserine. Theses substances are transferred to female uterus with spermatozoa during mating. Most amino acids increase distinctly at 30 min after the termination of mating (ATM) and then decline, suggesting active degradation of transferred proteins in the uterus. As found inBombyx, urea increases at the post-mating period, while ornithine shows a rather low concentration. Ornithine must be converted to glutamate. In this connection, it is notable that alanine rises markedly at 30 min following mating. As in the silkmoth, the energy metabolism of the fruit fly spermatozoa involves also arginine, ornithine, urea, and proline. These findings suggest that the occurrence of the arginine degradation cascade or related metabolic pathway in this insect.
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PMID:A comparative study on the arginine degradation cascade for sperm maturation ofBombyx mori andDrosophila melanogaster. 2419 Jul 5