Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molecular weights of trypsin and chymotrypsin purified from anchovy viscera were estimated to be 25.6 and 26.1 Kda, respectively, by SDS-PAGE. Both enzymes had their maximal activity at pH 9.0 and 45 degrees C for casein and at pH 8.0 and 45 degrees C for synthetic substrates. Trypsin hydrolyzed at the position of Arg22 and Lys29, and chymotrypsin did at the position of Phe1, Tyr16, Phe24, Phe25, and Tyr26 of insulin beta-chain. The K'm and kcat of trypsin were 50 microM and 1.84 microM-1 min-1 toward N-benzoyl-L-arginine-p-nitroanilide (BAPNA) and those of chymotrypsin were 89 microM and 10.0 microM-1min-1 toward N-succinyl-(Ala)2-Pro-Phe-p-nitroanilide. The activation energy of trypsin and chymotrypsin were estimated to be 14 Kcal/mol toward N-benzoyl-L-arginine-p-nitroanilide and 6.5 Kcal/mol toward benzoyl-L-tyrosine ethyl ester.
Comp Biochem Physiol B Biochem Mol Biol 1995 Nov
PMID:Comparison of trypsin and chymotrypsin from the viscera of anchovy, Engraulis japonica. 852 32

In vitro experiments are reported showing that NAD(P)H:(quinone acceptor) oxidoreductase (QR), purified from Glycine max seedlings, reduces Leu- and Met-enkephalin-tyrosinase oxidation products, in the presence of NADH or NADPH. QR was not capable to catalyze the reduction of N-acetyl-dopaquinone formed by the cation of mushroom tyrosinase on N-acetyl-L-tyrosine, while it was able to reduce dopachrome. The results support the hypothesis that QR can inhibit the formation of melanin-like compounds, as catalyzed by the action of tyrosinase on Leu-enkephalin and Met-enkephalin. It is proposed that, in the presence of NAD(P)H as the electron donor, the inhibition occurs by the specific conversion of the dopachrome-derivative into the reduced precursor, leucodopachrome-derivative.
Biochem Mol Biol Int 1995 Oct
PMID:Effect of NAD(P)H:quinone oxidoreductase on tyrosinase-mediated oxidation of opioid neuropeptides Leu-enkephalin and Met-enkephalin. 867 15

Tyrosine hydroxylase (TH) catalyzes the conversion of L-tyrosine to L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of dopamine. This report describes a missense point mutation in the human TH (hTH) gene in a girl presenting parkinsonian symptoms in early infancy and a very low level of the dopamine metabolite homovanillic acid in the CSF. DNA sequencing revealed a T614-to-C transition in exon 5 (L205P). Both parents and the patient's brother are heterozygous for the mutation. Site-directed mutagenesis and expression in different systems revealed that the recombinant mutant enzyme had a low homospecific activity, i.e. approximately 1.5% of wt-hTH in E. coli and approximately 16% in a cell-free in vitro transcription-translation system. When transiently expressed in human embryonic kidney (A293) cells a very low specific activity (approximately 0.3% of wt-hTH) and immunoreactive hTH (< 2%) was obtained. The expression studies are compatible with the severe clinical phenotype of the L205P homozygous patient carrying this recessively inherited mutation. Treatment with L-DOPA resulted in normalisation of the CSF homovanillic acid concentration and a sustained improvement in parkinsonian symptoms.
Hum Mol Genet 1996 Jul
PMID:Recessively inherited L-DOPA-responsive parkinsonism in infancy caused by a point mutation (L205P) in the tyrosine hydroxylase gene. 881 41

Phenoloxidase (PO) activity in the albumen gland (AG) and egg masses (EM) of Biomphalaria glabrata was assessed using high-performance liquid chromatography combined with electrochemical detection and colorimetric techniques. Both AG and EM extracts catalyzed the hydroxylation of L-tyrosine (monophenol oxidase activity, MPO) and oxidation of L-dopa (diphenol oxidase activity, DPO). However, no PO activity was found in the ovotestis. Both MPO and DPO activities in AG and EM were significantly inhibited by 1-phenyl-2-thiourea and inactivated by boiling. Approximately 35% of MPO and 44% of DPO activities were detected in the soluble fraction of homogenized EM, in contrast to that of homogenized AG, which contained about 5% and 12%, respectively, of MPO and DPO activities. N-acetyl-dopamine, a diphenolic compound, enhanced the hydroxylation of tyrosine by the PO. The presence of both MPO and DPO activities also was confirmed by the accelerated accumulation of dopachrome during incubation of EM extracts with L-tyrosine in the absence of ascorbate. Temperature and pH optima for this enzyme were 30 degrees C and 7.5, respectively. The potential roles of PO in egg formation in B glabrata are discussed.
Comp Biochem Physiol B Biochem Mol Biol 1996 Aug
PMID:Phenoloxidase activity in the reproductive system and egg masses of the pulmonate gastropod, Biomphalaria glabrata. 884 May 12

Pseudomonas aeruginosa was recently found to possess a cluster of structural genes encoding phenylalanine hydroxylase (PhhA), carbinolamine dehydratase (PhhB), and aromatic aminotransferase (PhhC). We now report the presence, in the flanking upstream region, of a divergently transcribed gene (phhR) encoding an activator protein. Inactivation of phhR markedly reduced expression of the structural genes. PhhR belongs to the large prokaryote family of sigma 54 enhancer-binding proteins, and activation of the phh operon by PhhR in P. aeruginosa required rpoN. The closest homologues of PhhR are the TyrR proteins from Escherichia coli and Haemophilus influenzae. E. coli TyrR is an unusual member of the homologue family in that the transcriptional units regulated by tyrR are driven by sigma 70 promoters. P. aeruginosa phhR was able to replace E. coli tyrR as a repressor of the aroF-tyrA operon (but not as an activator of mtr) in the heterologous E. coli system. Two regions that resemble E. coli TyrR boxes were identified in the intervening region between phhR and phhA. We propose that one or both boxes may be the target of PhhR acting as an autogenous repressor at a sigma 70 promoter in one direction. In the other direction, one or both boxes may be the upstream activator sequence targeted by PhhR to facilitate expression of the phh operon from a sigma 54 promoter. The phh operon was strongly induced in fructose- or glucose-based minimal medium by L-phenylalanine. Inactivation of phhR in P. aeruginosa abolished ability to utilize either L-phenylalanine or L-tyrosine as a sole source of carbon for growth.
Mol Microbiol 1996 Nov
PMID:PhhR, a divergently transcribed activator of the phenylalanine hydroxylase gene cluster of Pseudomonas aeruginosa. 893 33

Despite the importance of the substrate 4-hydroxyanisole in melanoma therapy, the kinetics of its oxidation catalyzed by tyrosinase has never been properly characterized. This approach is reported here for the first time. The applicability to 4-hydroxyanisole of the reaction mechanism of tyrosinase previously proposed for other monophenols has been corroborated. The Michaelis constant for the oxidation of 4-hydroxyanisole catalyzed by mushroom tyrosinase was (62 +/- 1.5) microM at pH 7 and increased when the pH decreased, reaching a value of (195 +/- 5) microM at pH 5.5. However the maximum steady-state rate, whose value was (0.54 +/- 0.01) microM/min, did not change with the pH. The apparent catalytic constant was (184 +/- 5) s-1, around twenty three times higher than that previously described for L-tyrosine (8 s-1).
Biochem Mol Biol Int 1997 May
PMID:Kinetic study of the oxidation of 4-hydroxyanisole catalyzed by tyrosinase. 916 22

Crotamine, a basic, myonecrotic, histamine-releasing neurotoxin, was isolated from Crotalus durissus terrificus venom. Carboxypeptidase A was shown to be activated by crotamine when acting upon N-carbobenzoxyglycil-L-phenylalanine. However the activity of carboxypeptidase B upon the substrate hippuryl-L-arginine was not enhanced by this toxin. Teh basic histamine releasers protamine and compound 48/80 also activated carboxypeptidase A. These three agents activated both alpha-chymotrypsin when acting upon acetyl-L-tyrosine ethyl ester and also five snake venom phospholipase-like myotoxins acting upon egg yolk phosphatidylcholine. These findings suggest that the action of these agents during histamine release may involve the participation of specific intermediary hydrolases which, upon activation, would enhance their cytolytic effects on the sequence of events which lead to granule extrusion and histamine release from mast cells.
Biochem Mol Biol Int 1997 Sep
PMID:The histamine releasers crotamine, protamine and compound 48/80 activate specific proteases and phospholipases A2. 930 35

The relationship between L-tyrosine catabolism and melanin formation was studied in the Vibrio cholerae strains ATCC 14035 and CECT 557. It is shown that both strains degrade L-tyrosine by the same pathway as eukaryotic cells, giving homogentisate as intermediate. ATCC 14035, an O1 strain, which is not able to grow using L-tyrosine as sole carbon and energy source, but it forms pyomelanin from homogentisate. The second strain, which is non-O1, is able to grow using L-tyrosine as sole carbon and energy source, but it does not form any pigment. Both strains contain all the enzymes involved in the L-tyrosine catabolism. The three late enzymes of the pathway, homogentisate oxygenase, maleylacetoacetate isomerase and fumarylacetoacetate hydrolase, are induced by L-tyrosine, but the degree of induction is much lower in the ATCC 14035 strain. Thus, the distal part of the pathway becomes the rate-limiting steps in the L-tyrosine catabolism, explaining homogentisate accumulation and pyomelanogenesis in this strain. It is proposed that V. cholerae might be a useful prokaryotic model to show that alkaptonuria and other diseases related to L-tyrosine metabolism could occur in animals even when no particular enzyme involved in that pathway is lacking.
Comp Biochem Physiol B Biochem Mol Biol 1998 Mar
PMID:Comparative tyrosine degradation in Vibrio cholerae strains. The strain ATCC 14035 as a prokaryotic melanogenic model of homogentisate-releasing cell. 973 39

Mobilization of intracellular Ca2+ is a critical cellular response to lysophosphatidic acid (LPA) in many cell types. Recent identification of endothelial differentiation gene (Edg) 2 and Edg4 as subtypes of G protein-coupled receptors for LPA allowed examination of the Ca2+ mobilization mediated specifically by each subtype. To reduce endogenous background levels while enhancing recombinant receptor-specific signals, the aequorin luminescence method was used to quantify cytoplasmic Ca2+ levels. In TAg-Jurkat T cells transiently co-transfected with apoaequorin and human Edg2 or Edg4 cDNA, LPA dose-dependently increased light emission triggered by increased Ca2+ bound to aequorin. N-Palmitoyl-L-serine-phosphoric acid and N-palmitoyl-L-tyrosine-phosphoric acid, which had been previously shown to be antagonists for Xenopus laevis LPA receptors, did not antagonize the Ca2+-mobilizing effects of Edg2 and Edg4. Surprisingly, they acted as agonists or partial agonists for Edg2 and Edg4. The Ca2+ mobilization by Edg2 and Edg4 was further characterized in stable transfectants of rat HTC4 hepatoma cells. By using the fura-2 fluorescence method, a difference in the kinetics of Ca2+ flux with Edg2 and Edg4 was observed. With Edg2, but not Edg4, the initial increase in the Ca2+ concentration was followed by a sustained influx of extracellular Ca2+. The coincident production of inositol phosphates and the inhibition of Ca2+ mobilization by the phospholipase C inhibitor U73122 strongly suggested that Edg2 and Edg4 mobilize Ca2+ through inositol trisphosphate generated by phospholipase C activation. Pertussis toxin almost completely blocked LPA-induced Ca2+ mobilization by Edg2 but only partially blocked that by Edg4, which suggests that Edg2 transduces Ca2+ mobilization largely through pertussis toxin-sensitive Gi proteins, whereas Edg4 requires both Gi and Gq.
Mol Pharmacol 1998 Nov
PMID:Recombinant human G protein-coupled lysophosphatidic acid receptors mediate intracellular calcium mobilization. 980 23

We previously reported that T3(3,3',5-triiodo-L-thyronine) acutely increases sodium currents (INa) in neonatal rat myocytes. Here we compare the effects of several thyroid hormone analogs, including T4(3,3',5,5'-tetraiodo-L-thyronine), rT3(3,3',5'-triiodo-L-thyronine), D-T3(3,3',5-triiodo-D-thyronine), 3,5-T2(3,5-diiodo-L-thyronine), DIT (3,5-diiodo-L-tyrosine), MIT (3-monoiodo-L-tyrosine), tetrac (3,3',5,5'-tetraiodo-thyroacetic acid), triac (3, 3',5-triiodo-thyroacetic acid), and tyrosine, on INa in cultured neonatal rat myocytes (n ranged from 9 to 28 for each comparison). T4, T3, 3,5-T2, and DIT (10 n m) all increased current density relative to control to a similar degree: to 1.22+/-0.2, 1.21+/-0.03, 1.16+/-0.02 and 1.16+/-0.03, respectively, P<0.05. In contrast, thyroid hormone analogs with an altered side group of the inner iodophenyl ring, including tetrac, triac, and D-T3, had no effect on INa nor did rT3, MIT or tyrosine. Pretreatment with rT3 inhibited the effects of T4, T3, 3,5-T2, and DIT. Conversely, the dose-dependent inhibitory effect of amiodarone, an iodinated benzofuran derivative that antagonizes thyroid hormone actions, on INa was blocked when myocytes were pretreated with T3(100 n m, n=3), suggesting an interaction of T3 with amiodarone. The enhancement of INa by T3 and 3, 5-T2 could not be blocked by propranolol, suggesting that the effects are not mediated through beta -adrenergic signaling pathways. In conclusion, the present results suggest that the acute effects of thyroid hormone and analogs on cardiac INa are mediated by a non-genomic thyroid hormone receptor with a unique structure-activity relationship.
J Mol Cell Cardiol 1999 Apr
PMID:Acute effects of thyroid hormone analogs on sodium currents in neonatal rat myocytes. 1032 15


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