PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Biosynthetic Pathways”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1986

Phospholipid base exchange in human leukocyte membranes: quantitation and correlation with other phospholipid biosynthetic pathways.

The biosynthesis of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) by base-exchange reactions, and of PC and PE by the CDP pathways, was assessed in the membrane phospholipids of human leukocytes (neutrophils, lymphocytes, T lymphocytes, non-T lymphocytes, and monocytes). Of the three base-exchange activities, ethanolamine exchange was the highest and choline exchange the lowest in each leukocyte membrane. In the CDP pathways, ethanolaminephosphotransferase (EPT) and cholinephosphotransferase (CPT) had comparable activities. Among subpopulations of leukocytes, T lymphocytes showed the highest levels of each enzyme activity, and neutrophils showed the least. In contrast to the enzymes of the CDP pathways, each base-exchange activity was directly proportional to the Ca2+ concentration, but markedly inhibited by Mg2+. Despite this Ca2+ dependence, the base-exchange activities were increased in a dose-dependent manner by calmodulin antagonists and, except for ethanolamine exchange, inhibited by the addition of calmodulin; EPT and CPT activities were only slightly inhibited by calmodulin antagonists and were unaffected by calmodulin. PE formation in both neutrophil and lymphocyte base-exchange reactions was enhanced in a dose-dependent manner by the presence of low concentrations of bioactive stimulants (zymosan, 0.05-0.2 mg/ml; Con A, 0.5-2 micrograms/ml), while EPT and CPT activities were not increased by these cell stimulants. Taken together, our data suggest that base-exchange activity, the biological significance of which has been hitherto unclear, may be related to cell activation; in contrast, the CDP pathways appear primarily to involve the constitutive biosynthesis of phospholipids. Our data further suggest that ethanolamine required for base-exchange reactions is a precursor of PE, N-transmethylation of which can serve as a source of cell activation, leading to production of arachidonic through PC by mediation of phospholipase A2 activity.

Calcium↗
PubMed1977

Distribution of prostaglandin biosynthetic pathways in several rat tissues. Formation of 6-ketoprostaglandin F1alpha.

The capacity of homogenates of rat lung, liver, spleen, whole stomach, stomach fundus, kidney and heart to form prostaglandin E2, F2alpha, D2, thromboxane B2 and 6-ketoprostaglandin F1alpha was investigated. All products were quantitated by mass spectrometry. The results demonstrated interesting differences between tissues in the direction of the 'prostaglandin synthetase' to specific products (e.g. as in spleen and stomach).

Animals↗
PubMed1978

Distribution of prostaglandin biosynthetic pathways in organs and tissues of the fetal lamb.

Five prostaglandins, i.e. prostaglandins E2, F2alpha and D2, 6-keto-prostaglandin F1alpha and thromboxane B2, were measured by mass spectrometry. Homogenates of fetal lamb brain, lung, liver, spleen and kidney and the ductus arteriosus, aorta and pulmonary artery formed different amounts of each product. Although the main prostaglandin in the fetal organs was prostaglandin E2, arterial tissue formed mostly 6-keto-prostaglandin F1alpha. These results demonstrate significant differences between organs and tissues in the relative direction of the 'prostaglandin synthetase' enzyme complex.

Animals↗
PubMed1982

Linkage of the isoprenoid biosynthetic pathway with induction of DNA synthesis in mouse lymphocytes. Effects of compactin on mitogen-induced lymphocytes in serum-free medium.

Concanavalin A induction of DNA synthesis in mouse spleen lymphocytes cultured in serum-free medium was shown to be very sensitive to inhibition by compactin (ML-236B), a specific competitive inhibitor of hydroxymethylglutaryl-CoA reductase. As low as 0.1 microM compactin could give 98% inhibition of mitogen induction of a 5.10(6) cells/ml culture. This inhibition could be reversed completely by addition of exogenous mevalonate, but could not be reversed by either exogenous cholesterol or isopentenyladenine. Oxygenated sterol inhibition of mitogen-induced DNA synthesis could be reversed by cholesterol or by mevalonate, whereas cyclic AMP inhibition could not be reversed by either compound. These results suggest that endogenous cholesterol production is a necessary but not sufficient factor co-ordinated with mitogen-induced DNA synthesis, and that the presence of some additional product of mevalonate metabolism is involved also. Isopentenyladenine, though, did not have as significant effect of alleviating any of the above inhibitions. Since mevalonate could not relieve cyclic AMP inhibition, but could overcome compactin inhibition, cyclic AMP inhibition cannot be explained as due only to blockage of mevalonate production.

Animals↗
PubMed1989

Analysis of endothelin related peptides in culture supernatant of porcine aortic endothelial cells: evidence for biosynthetic pathway of endothelin-1.

We investigated the molecular forms of endothelin (ET) related peptides in culture supernatant of porcine aortic endothelial cells by high performance liquid chromatography coupled with radioimmunoassays for ET related peptides. We isolated and sequenced a C-terminal peptide (big ET-1(22-39] of big ET-1(1-39) and its N-terminal truncated form (big ET-1(23-39] in addition to ET-1(1-21) and its oxidized form, [Met7 (0)]ET-1(1-21). The total contents of the two C-terminal peptides of big ET-1(1-39) are approximately equal to those of ET-1(1-21) and its oxidized form on a molar basis in the culture supernatant. Furthermore, we isolated big ET-1(1-39) although its content is approximately 2% of that of ET-1(1-21). These results strongly suggest that ET-1(1-21) and big ET-1(22-39) are generated from big ET-1(1-39) by specific processing between Trp21-Val22.

Animals↗
PubMed1985

The influence of carbamazepine on the heme biosynthetic pathway.

Carbamazepine, a drug which is widely used in neurological diseases, has a porphyrogenic effect in chick embryo liver cells in culture. It increased the concentration of cellular porphyrins by 80-fold and delta-aminolevulinate synthase activity by 4-fold. The increase in the accumulation of porphyrins preceded that of ALAS activity. Measurements of the activities of aminolevulinate dehydrase, porphobilinogen deaminase, and uroporphyrinogen decarboxylase showed that C inhibits UROD up to nearly 50% and PBGD activity up to 20%, but does not affect the activity of ALAD. The pattern of accumulation of porphyrins, mainly uro- and heptacarboxylporphyrin, is compatible with an inhibition of UROD. We may, therefore, conclude that the porphyrogenic effect of C in monolayers of chick embryo liver cells is the result of its inhibitory effect on the activity of UROD.

5-Aminolevulinate Synthetase↗