Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.5.5 (CPS)
 1,262 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of a number of enzymes in rat liver have been measured at different times during adulthood and senescence and expressed as a percentage of maximal activity that can be attained after hormonal stimulation. Three different profiles can be detected. Type I profile shows decreasing activities during adolescence (1--3 months of age), increasing activities during adulthood (4--12 months of age) and relatively high activities thereafter. Enzymes of this group are carbamoyl-phosphate synthase and arginase; DNA content shows the same pattern. Type II profile shows decreasing activities during adolescence and relatively low activities thereafter. Enzymes of this group are tyrosine aminotransferase, glucose-6-phosphatase, and glucokinase. Type III profile shows relatively high activities during adolescence, adulthood and senescence. Enzymes of this group are ornithine transcarbamoylase, glutamate dehydrogenase and hexokinase. Some enzymes are constant with age in females, but slowly decrease in activity with age in males; decreasing levels of androgens and possibly also thyroid hormones can explain this decrease in males. Decreasing activities of carbamoyl-phosphate synthase and arginase during adolescence can be attributed to a depressant effect of gonadal hormones. The difference between relatively high and relatively low basal activities of enzymes in adult and senescent rats corresponds with their relatively long and short half-lives, respectively. This relation implicates a similar rate of synthesis of glucocorticosteroid hormone-dependent enzymes.
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PMID:Changes in the control of enzyme clusters in the liver of adult and senescent rats. 611 95

Enzyme activities and DNA content have been measure in axolotl liver during the metamorphic period (4-8 months after spawning). Three different types of enzyme activity profiles were observed. In the type I profile (carbamoyl-phosphate synthase, arginase, ornithine transcarbamoylase, and glutamate dehydrogenase) enzyme activity is high in the youngest animals studied, and shows a minimum at 5 months followed by a maximum at 8 months of age. Thereafter activities do not change or slightly decrease. In the type II profile (tyrosine aminotransferase, glucose-6-phosphatase) enzyme activity shows a peak at 5 months of age and is low thereafter. Hexokinase, the enzyme with a type III profile, shows high activity throughout the metamorphic period. DNA content remains high throughout the metamorphic period but decreases 50% between 9 and 12 months of age, probably due to an increase in the size of the hepatocytes. No glucokinase activity was detected. High activities of cluster II enzymes represent early metamorphic events, while the rising part of cluster I is associated with late metamorphic events. The apparent molecular specific activity increases during natural development between 5 and 9 months of age, or precociously, upon thyroid hormone treatment. This change in apparent molecular specific activity is correlated to the advent of ureotelism.
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PMID:Enzyme clusters during the metamorphic period of Ambystoma mexicanum: role of thyroid hormone. 612 71

The role of glucocorticosteroid and thyroid hormone and of glucagon and insulin in the pre- and postnatal developmental formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase, glucose-6-phosphatase, hexokinase and glucokinase activities in rat liver was investigated. Glucocorticosteroids and a low insulin/glucagon ratio always stimulate formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase and glucose-6-phosphatase, while glucocorticosteroids and a high insulin/glucagon ratio stimulate formation of glucokinase. Thyroid hormone stimulates the formation of carbamoyl-phosphate synthase, arginase and tyrosine aminotransferase only before birth, whereas it stimulates the formation of glutamate dehydrogenase and glucose-6-phosphatase both before and after birth. Ornithine transcarbamoylase activity is depressed after thyroid-hormone treatment before and after birth. DNA content is always decreased by glucocorticosteroids and increased by thyroid hormone. The effect of these hormones on hexokinase is complex, probably due to different responses of the constitutive isozymes. With the exception of the effects of thyroid hormone on carbamoyl-phosphate synthase, arginase and tyrosine aminotransferase before birth, which may be indirect, the responses of enzyme activities and DNA content to treatment with glucocorticosteroid hormones, glucagon, insulin and thyroid hormone are qualitatively the same in fetuses, neonates, sucklings, weanlings and adults. Thus, the developmental profiles of the enzyme clusters reflect the changing levels of the relevant hormones. The enzymes that are stimulated by glucocorticosteroids and the insulin/glucagon ratio show increases in enzyme activity perinatally and around weaning, and relatively low activities in between, while those enzymes that are additionally stimulated by thyroid hormone differ in exhibiting relatively high activities between birth and weaning.
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PMID:Multihormonal control of enzyme clusters in rat liver ontogenesis. II. Role of glucocorticosteroid and thyroid hormone and of glucagon and insulin. 702 60

The role of glucocorticosteroid hormones in the developmental formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase, glucose-6-phosphatase, hexokinase and glucokinase activities in rat liver was investigated. Steroid hormone producing glands were either inactivated by hypophysectomy (before birth) or removed by adrenalectomy and/or gonadectomy (after birth). These procedures strongly depressed corticosterone levels. Furthermore, they decreased enzyme activities when performed before birth or after the second postnatal week. However, adrenalectomy at 1 week of age was less effective: the developmental increases in carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, tyrosine aminotransferase and glucose-6-phosphatase activity persisted despite the absence of increasing levels of circulating corticosterone.
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PMID:Multihormonal control of enzyme clusters in rat liver ontogenesis. I. Effects of adrenalectomy and gonadectomy. 727 92

Hepatocyte proliferation and differentiation occur simultaneously during late mammalian gestation. We hypothesized that regulation of hepatocyte growth and differentiation would be coordinated in late gestation fetal hepatocyte cultures such that proliferation would be most active in a population of less well-differentiated cells. Cultured fetal hepatocytes (embryonic d 19 and 21; E19 and E21) were studied using double staining immunofluorescent microscopy. Differentiation was assessed as staining for alpha-fetoprotein (AFP), three markers of enzymic differentiation (glucokinase [GK], phosphoenolpyruvate carboxykinase [PEPCK], and carbamoyl phosphate synthase [CPS]), and a hepatocyte cell-cell adhesion molecule (C-CAM). Proliferation was assessed using immunocytochemical detection of proliferating cell nuclear antigen (PCNA) or 5-bromo-2'-deoxy-uridine (BrdU) incorporation into DNA. Fetal hepatocyte cultures consisted of a heterogeneous population of cells, slightly more than half of which were proliferative under defined, growth factor-free conditions. These cultures were heterogeneous for AFP expression. There was no correlation between the expression of AFP and PCNA or AFP and S-phase entry (BrdU staining) during the first 48 h in culture. Similar results were obtained in staining for the enzymic differentiation markers and C-CAM. In addition, the differentiation status of cultured fetal hepatocytes was unrelated to a presumed indicator of mature growth regulation, mitogenic responsiveness to transforming growth factor alpha (TGFalpha), and hepatocyte growth factor (HGF). Finally, absence of any correlation between proliferation and differentiated phenotype was supported by in vivo studies using staining for PCNA, AFP, CPS, and PEPCK in liver sections. These results indicate that the developmental program governing differentiation of late gestation fetal rat hepatocytes is independent from mechanisms controlling proliferation.
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PMID:The relationship between differentiation and proliferation in late gestation fetal rat hepatocytes. 1040 Jan 28