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Biomedical subjects

S Udenfriend

Publications and source records attributed to S Udenfriend.

At least 19 recordsLinked to original sources
PubMed1992

Phosphatidylinositol-glycan (PI-G)-anchored membrane proteins: requirement of ATP and GTP for translation-independent COOH-terminal processing.

Placental alkaline phosphatase (PLAP) belongs to a class of proteins that are anchored to the plasma membrane by a COOH-terminal phosphatidylinositol-glycan (PI-G) moiety. Nascent forms of such proteins undergo NH2- and COOH-terminal processing to yield the mature PI-G-tailed proteins. We previously introduced a shortened engineered form of preproPLAP (preprominiPLAP) that permits monitoring in cell-free preparations its sequential processing to the pro form and then to the mature PI-G-tailed form. Previous studies were carried out by synthesizing the preproprotein cotranslationally in the presence of rough microsomal membranes (RM). Because of the complexity of the cotranslational system it was not possible to determine whether cofactors were required for processing. We have now prepared RM that are preloaded with prominiPLAP but contain little mature PI-G-tailed miniPLAP. Maximal processing requires supplementation with both ATP and GTP. Inhibitors of PI-G biosynthesis do not affect processing. Since cleavage and PI-G addition are presumably catalyzed by a transamidase, the nucleoside triphosphate requirements suggest that there are additional steps in prominiPLAP processing prior to transamidation with PI-G. These may involve translocation of the pro protein in a proper conformational state to the transamidase site.

Adenosine Triphosphate↗
PubMed1979

On betaH-Leu5-endorphin and schizophrenia.

A previously unknown peptide, betaH-Leu5-endorphin, has been reported in the dialysates of schizophrenic patients. Accordingly, hemofiltrates from two schizophrenic and two control patients were examined for the presence of betaH-Leu5-endorphin. The opioid peptides were detected by a radioreceptor assay after separation and identification by gel filtration and high-performance liquid chromatography. With a detection limit of 30 pmole/L of hemofiltrate, no betaH-Leu5-endorphin or Met5-endorphin was found in controls or in patients. Whatever the possible involvement of endorphins in schizophrenic behavior, they are not present at detectable levels in the hemofiltrates of two well-characterized schizophrenic patients, thereby casting doubt on a general relationship of Leu-endorphin and schizophrenia.

Adult↗
PubMed1979

Isolation of the opioid heptapeptide Met-enkephalin [Arg6,Phe7] from bovine adrenal medullary granules and striatum.

Bovine adrenal chromaffin granules have been shown to contain, in addition to Met-enkephalin and Leu-enkephalin, at least three small peptides with opiate receptor activity. One of these adrenal peptides has been purified to homogeneity and its sequence was shown to be Met-enkephalin-[Arg6,Phe&]. This heptapeptide was also found in beef striatal extracts in amounts comparable to those of Leu-enkephalin.

Adrenal Medulla↗
PubMed1979

Purification to homogeneity of camel pituitary pro-opiocortin, the common precursor of opioid peptides and corticotropin.

Pro-opiocortin was purified from camel pituitaries by procedures including high-performance liquid chromatography. The precursor relationship of the pure protein to the opioid peptides and to corticotropin was confirmed. Partial chemical analysis consisting of amino acid analysis and tryptic peptide mapping was carried out with the aid of sensitive fluorescence detection.

Adrenocorticotropic Hormone↗
PubMed1979

Separation of opioid peptides utilizing high performance liquid chromatography.

Chromatographic procedures have been developed for resolving all of the known enkephalins and endorphins on a single column. The effect of eluant pH on the retention times and separation of the enkephalins and beta-endorphin was determined. By combining these separations with a sensitive radioreceptor assay it is possible to assay all of the opioid peptides in the pituitary gland or in various regions of the brain from individual small laboratory animals.

Amino Acid Sequence↗
PubMed1979

An analyst in biomedical research.

Fluorescamine is a nonfluorescent substance that reacts with primary amines to yield intensely fluorescent products. We have utilized high performance liquid chromatography along with fluorescamine assay for many studies relating to the biochemistry of the opioid peptides.

Endorphins↗
PubMed1979

Effect of guanethidine on collagen biosynthesis in blood vessels of hypertensive rats.

The effect of guanethidine on collagen biosynthesis in the aorta and mesenteric artery was investigated in desoxycorticosterone acetate (DOCA)-salt hypertensive rats. Prolyl hydroxylase activity (EC 1.14.11.2; proline, 2-oxoglutarate dioxygenase) and 14C-proline incorporation into collagen, two markers of collagen biosynthesis, were significantly increased in blood vessels of hypertensive rats compared with those of controls. When guanethidine (5 mg/kg, i.p.) was given daily to the hypertensive rats for 4 weeks, the blood pressure was decreased to 150 +/- 7 mm Hg, whereas the blood pressure of the untreated hypertensive rats was 218 +/- 10 mm Hg. Prolyl hydroxylase activity in the aorta and mesenteric artery and 14C-proline incorporation into aortic collagen were significantly reduced concomitant with the decrease in blood pressure. These results suggest that the decrease in vascular collagen biosynthesis in hypertensive rats treated with guanethidine is related to the lowering of their blood pressure.

Animals↗
PubMed1978

Binding assay for opioid peptides with neuroblastoma x glioma hybrid cells: specificity of the receptor site.

A sensitive and rapid radioreceptor assay has been developed to monitor opioid peptides in column effluents. It is based on competitive binding to NG 108-15 cells using [3H-Tyr]Leu-enkephalin as the displaced ligand. The specificity of binding to the cells of naturally occurring opioid peptides and synthetic analogs has been shown to be similar to that found with synaptic plasma membranes.

Animals↗
PubMed1978

Increased turnover of arterial collagen in hypertensive rats.

The turnover of total collagen in several tissues of 12-week-old normotensive and hypertensive rats was estimated by using tritium-labeled proline as a precursor. The effect of reutilization of the label was minimized by treatment with large doses of unlabeled proline subsequent to administering the radioactive imino acid. The collagen from skin, tail tendon, aorta, and mesenteric artery in normotensive animals had a half-life of about 60--70 days. In hypertensive animals the half-lives of skin and tail tendon collagen were unchanged but the half-lives of collagen in the aorta and mesenteric artery were reduced to 17 days.

Animals↗
PubMed1978

Characterization of pro-opiocortin, a precursor to opioid peptides and corticotropin.

The high molecular weight (approximately 30,000) precursor to opioid activity (pro-opiocortin) previously detected in extracts of rat pituitary was digested with trypsin and the resulting peptide mixture was resolved by high-performance reverse-phase chromatography. A peak of opioid activity was eluted at the position of the nonapeptide beta-LPH (61-69), which was also the same fragment obtained by trypsin digestion of betas-lipotropin or beta-endorphin. This identified the protein as a precursor to the endorphins and Met-enkephalin. No activity was detected in the position corresponding to the Leu5 analog of betas-LPH (61-69), thus ruling out the possibility of a beta-lipotropin-like precursor to Leu-enkephalin in pituitary extracts. Pro-opiocortin and beta-lipotropin are present in rat pituitary extracts in comparable amounts, approximately 10 pmol/mg of tissue.

Adrenocorticotropic Hormone↗
PubMed1978

Expression of collagen biosynthetic activities in lymphocytic cells.

Immunoglobulin-producing Merwin plasma cells, MPC-11, have been found to contain proplyl hydroxylase (prolyl-glycyl-peptide,2-oxoglutarate:oxygen oxidoreductase; EC 1.14.11.2) activity and its crossreacting protein, as well as hydroxyproline and a collagenous protein that could not be classified as type I, II, or III collagen. Friend leukemic cells, on the other hand, contained only prolyl hydroxylase. Thymus-derived (T) lymphocytes and bone-marrow-derived (B) lymphocytes freshly isolated from BALB/c mice expressed low but significant prolyl hydroxylase activity. Upon stimulation with phytohemagglutinin, the enzyme activity in T cells increased 22- to 29-fold. Crossreacting protein was also increased and appeared more stable than the prolyl hydroxylase. The effect of lipopolysaccharide stimulation on B cells uas similar but not as pronounced. Thus, even when not accompanied by other collagen biosynthetic activities, prolyl hydroxylase is present in all cells of hematologic origin.

Animals↗
PubMed1978

Prolyl hydroxylase half reaction: peptidyl prolyl-independent decarboxylation of alpha-ketoglutarate.

Prolyl hydroxylase (proline,2-oxoglutarate dioxygenase, EC 1.14.11.2) is a mixed-function oxygenase that hydroxylates peptidyl proline with the simultaneous and stoichiometric decarboxylation of alpha-ketoglutarate to succinate and CO2. It has been found that highly purified preparations of the enzyme can decarboxylate alpha-ketoglutarate in the absence of a peptidyl proline substrate. The uncoupled decarboxylation proceeds at only a fraction of the rate of the whole reaction and for study requires substrate quantities of the pure enzyme, as well as oxygen, ferrous ion, and ascorbate. No hydroxyproline is formed under these conditions. Immobilized antiserum to prolyl hydroxylase was found to remove both activities from enzyme preparations. However, addition of free antiserum during incubation inhibits only the complete reaction. Poly(L-proline), a specific inhibitor of prolyl hydroxylation, enhances the uncoupled decarboxylation of alpha-ketoglutarate without itself being hydroxylated. All of these findings prove that alpha-ketoglutarate can serve as substrate in the absence of peptidyl proline and is most likely the initial site of attack by oxygen. In the coupled reaction an oxidized form of the keto acid, perhaps a peroxy acid, then attacks prolyl residues in the unhydroxylated substrate.

Animals↗