Comparative Studies on Bovine and Guinea Pig Tyrosine Hydroxylase

Petrack, Barbara; Fetzer, Valentina; Altiere, Ralph J.

doi:10.1016/b978-0-08-017922-3.50015-0

Cited by 9 publications

(15 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Only the completely reduced (tetrahydro) form of biopterin supports NOS coupling of NADPH oxidation to NO synthesis (52). Because NOS catalysis is associated with oxidation of BH 4 (53,54) and ascorbic acid has been proposed to maintain BH 4 in a reduced state (55), one might speculate that ascorbic acid simply maintains BH 4 in its reduced state. Indeed, our experiments with bovine eNOS from Sf9 cells would tend to support such an argument because ascorbic acid was ineffective with saturating BH 4 levels and GSH could substitute for BH 4 .…”

Section: Discussionmentioning

confidence: 99%

Ascorbic Acid Enhances Endothelial Nitric-oxide Synthase Activity by Increasing Intracellular Tetrahydrobiopterin

Huang¹,

Vita²,

Venema³

et al. 2000

Journal of Biological Chemistry

337

186

View full text Add to dashboard Cite

Ascorbic acid enhances NO bioactivity in patients with vascular disease through unclear mechanism(s).We investigated the role of intracellular ascorbic acid in endothelium-derived NO bioactivity. Incubation of porcine aortic endothelial cells (PAECs) with ascorbic acid produced time-and dose-dependent intracellular ascorbic acid accumulation that enhanced NO bioactivity by 70% measured as A23187-induced cGMP accumulation. This effect was due to enhanced NO production because ascorbate stimulated both PAEC nitrogen oxide (NO 2 ؊ ؉ NO 3 Ϫ ) production and L-arginine to L-citrulline conversion by 59 and 72%, respectively, without altering the cGMP response to authentic NO. Ascorbic acid also stimulated the catalytic activity of eNOS derived from either PAEC membrane fractions or baculovirus-infected Sf9 cells. Ascorbic acid enhanced bovine eNOS V max by ϳ50% without altering the K m for L-arginine. The effect of ascorbate was tetrahydrobiopterin (BH 4 )-dependent, because ascorbate was ineffective with BH 4 concentrations >10 M or in PAECs treated with sepiapterin to increase intracellular BH 4 . The effect of ascorbic acid was also specific because A23187-stimulated cGMP accumulation in PAECs was insensitive to intracellular glutathione manipulation and only ascorbic acid, not glutathione, increased the intracellular concentration of BH 4 . These data suggest that ascorbic acid enhances NO bioactivity in a BH 4 -dependent manner by increasing intracellular BH 4 content.Nitric oxide is produced from L-arginine in the vascular endothelium by the endothelial isoform of nitric-oxide synthase (NOS).1 Endothelial production of NO is crucial in the control of vascular tone (1), arterial pressure (2-4), smooth muscle cell proliferation (5, 6), and platelet adhesion to the endothelial surface (7). Impaired endothelium-derived NO bioactivity is a common feature of many vascular diseases (8 -10) that is thought to contribute to their clinical manifestations (11,12).The action of NO is particularly sensitive to the local availability of superoxide. Both endothelial elaboration of NO and arterial relaxation in response to nitrovasodilators are dependent upon intact copper-zinc superoxide dismutase (SOD) activity (13,14). Animal models of hypercholesterolemia (15, 16) and hypertension (17) demonstrate an excess vascular superoxide flux that is linked to reduced NO bioactivity. Conversely, increasing vascular SOD activity enhances NO-mediated arterial relaxation in experimental models of atherosclerosis (18,19) and hypertension (17). Thus, scavenging superoxide has important implications for NO bioactivity under both normal and pathologic conditions. Ascorbic acid also efficiently scavenges superoxide (20) and numerous studies in a host of pathologic conditions such as diabetes (21), hypercholesterolemia (22), smoking (23), and hypertension (24) indicate that NO bioactivity is improved by parenteral ascorbic acid at supraphysiologic concentrations (ϳ10 mM). We have observed enhanced NO bioactivity in atherosclerotic patients aft...

show abstract

Section: Discussionmentioning

confidence: 99%

Ascorbic Acid Enhances Endothelial Nitric-oxide Synthase Activity by Increasing Intracellular Tetrahydrobiopterin

Huang¹,

Vita²,

Venema³

et al. 2000

Journal of Biological Chemistry

337

186

View full text Add to dashboard Cite

show abstract

“…By immunocytochemistry, both PMTase and TyrOHase have been seen to be associated with chromaffin granules (5-9), and one report shows TyrOHase to be localized on microtubules (8). In purification procedures, 5-90% of the TyrOHase activity and 15-20%o of the PMTase activity in the adrenal medulla have been reported to be found in the particulate fraction (10)(11)(12)(13). TyrOHase is also found in chromaffin granule membranes, where it is the major substrate for protein kinase (14).…”

mentioning

confidence: 99%

Restricted diffusion of tyrosine hydroxylase and phenylethanolamine N-methyltransferase from digitonin-permeabilized adrenal chromaffin cells.

Kelner¹,

Morita²,

Rossen³

et al. 1986

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosie,tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14. 16.2] and phenylethanolamine N-methyltransferase (PMTase; S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1. 1.28) are involved in catecholamine biosynthesis and are considered soluble proteins. However, they may actually be localized on the surface of the chromaffin granule. We have used the detergent digitonin to permeabilize the plasma membrane of cultured adrenal chromaffln cells to investigate the subcellular localization of TyrOHase and PMTase. A digitonin titration of the release of proteins and catecholamines revealed the existence of at least three subcellular compartments that are distinguished by their digitonin sensitivity: (i) soluble proteins, which were released upon treatment of the cells with low digitonin concentrations (S jM), (ii) a "digitonin-sensitive" cytoplasnic protein pool, which required higher concentrations of digitonin for release (10 ,uM) and included TyrOHase and PMTase, and (iii) the chromaffln granule, which was insensitive to digitonin. Analysis of the rates of release of all of these proteins revealed that the rate of TyrOHase and PMTase release was slower at 10 IAM than at 40 jaM digitonin, while the rates of release of the other proteins were similar at both concentrations and varied in proportion to their respective sizes. Treatment with cytoskeletal disrupting agents had no effect on TyrOHase or PMTase eftlux. These data suggest that TyrOHase and PMTase are in a detergent-labile association in the cell. This is consistent with the concept that TyrOHase and PMTase may be localized on the surface of the chromffin granule.In epinephrine-forming cells of the adrenal medulla, the catecholamine biosynthetic pathway is composed of four enzymes, tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine,tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2], aromatic amino acid decarboxylase (aromatic L-amino acid carboxy-lyase, EC 4.1.1.28), dopamine ,B-hydroxylase [dopamine l3-monooxygenase; 3,4-dihydroxyphenethylamine, ascorbate:oxygen oxidoreductase (P-hydroxylating), EC 1.14.17.1] and phenylethanolamine N-methyltransferase (PMTase; Sadenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1.1.28). Dopamine o-hydroxylase is localized in the interior of the chromaffin granule and on the internal face of the granule membrane (1), while TyrOHase, aromatic amino acid decarboxylase, and PMTase are generally considered to be "soluble" cytoplasmic enzymes and ate synthesized on free ribosomes (2-4). However, morphological and subcellular fractionation studies suggest the possible particulate localization of PMTase and TyrOHase, perhaps on the surface of the chromaffmi granule. By immunocytochemistry, both PMTase and TyrOHase have been seen to be associated with chromaffin granules (5-9), and one report shows TyrOHase to be localized on microtubules (8). In purification procedur...

show abstract

“…The medulla was homogenized in 20 mM potassium phosphate buffer (pH 6.5) and cellular debris was removed. The homogenate was centrifuged at 40,000 X g for 60 min, yielding active enzyme in both the supernatant ["high-molecular-weight" form (16) We purified the sediment enzyme by treating the sediment with trypsin as described by Petrack et al (17) and then centrifuging at 100,000 X g for 60 min. The supernatant was collected, treated with ammonium sulfate, and sequentially chromatographed through a Sephadex G-200 and then through a Sephadex G-100 column.…”

mentioning

confidence: 99%

Immunochemical Demonstration of Increased Accumulation of Tyrosine Hydroxylase Protein in Sympathetic Ganglia and Adrenal Medulla Elicited by Reserpine

Joh

Geghman

Reis

1973

Proc. Natl. Acad. Sci. U.S.A.

238

View full text Add to dashboard Cite

Chronic administration of reserpine to rats increases, in sympathetic ganglia and adrenal medulla, the activity of tyrosine hydroxylase (EC 1.14.3.x), the enzyme catalyzing the rate-limiting step in the biosynthesis of catecholamines. Immunochemical titration of the enzyme in both adrenal gland and innervated superior cervical ganglia demonstrates that enhanced enzyme activity is entirely attributable to accumulation of more specific enzyme protein and riot activation of preexistent enzyme molecules.

show abstract

Comparative Studies on Bovine and Guinea Pig Tyrosine Hydroxylase

Cited by 9 publications

References 6 publications

Ascorbic Acid Enhances Endothelial Nitric-oxide Synthase Activity by Increasing Intracellular Tetrahydrobiopterin

Ascorbic Acid Enhances Endothelial Nitric-oxide Synthase Activity by Increasing Intracellular Tetrahydrobiopterin

Restricted diffusion of tyrosine hydroxylase and phenylethanolamine N-methyltransferase from digitonin-permeabilized adrenal chromaffin cells.

Immunochemical Demonstration of Increased Accumulation of Tyrosine Hydroxylase Protein in Sympathetic Ganglia and Adrenal Medulla Elicited by Reserpine

Contact Info

Product

Resources

About