Purification of tyrosine hydroxylase by high-pressure liquid chromatography

Our study of tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2) from rabbit adrenals has identified two major requirements which are likely to be of general application for the optimal purification and recovery of enzyme activity consequent to high-pressure liquid chromatography: (i) recovery of activity is maximized by pretreatment of the high-pressure liquid chromatography column before each use with protein to saturate high affinity, nonspecific sites exposed by the methanol used for washing, and storage of the column. (ii) Both purification and recovery are critically dependent upon the molarity of the mobile phase buffer. Examination of high-pressure liquid chromatography purified rabbit adrenal tyrosine hydroxylase by nondenaturing gel electrophoresis indicated that tyrosine hydroxylase activity was associated with one of the two protein bands in the gel. Thus, the convenient purification procedure described in this report leads to preparative amounts of tyrosine hydroxylase which is approximately 50% homogeneous.     

Purification and characterisation of tyrosine decarboxylase and aromatic-L-amino-acid decarboxylase

Microbial tyrosine decarboxylase (EC 4.1.1.25) and mammalian aromatic-L-amino-acid decarboxylase (EC 4.1.1.28) catalyse the formation of tyramine from L-tyrosine. These enzymes were characterised after isolation to purity by methods including fast polymer liquid chromatography (FPLC). Tyrosine decarboxylase was isolated from Streptococcus faecalis by FPLC anion exchange chromatography (11-times purification; 72% recovery; 23.2 U/mg protein). FPLC on Phenyl-Superose resulted in purification to 115 U/mg protein. Aromatic-L-amino-acid decarboxylase was isolated from pig kidney by ammonium sulfate fractionation, DEAE chromatography, and FPLC anion exchange chromatography (21-times purification; 22% recovery; 0.71 U/mg protein). By FPLC chromatofocusing, tyrosine decarboxylase eluted at pH 4.3 and aromatic-L-amino-acid decarboxylase at pH 5.0. Isoelectric focusing of tyrosine decarboxylase gave two bands (pI 4.4 and 4.5). With pyridoxal 5'-phosphate removed by ultrafiltration, only one band (pI 4.4) appeared, and SDS polyacrylamide electrophoresis confirmed the purity. FPLC gel filtration resulted in molecular weights 143,000 and 86,000, respectively, for tyrosine decarboxylase and aromatic-L-amino-acid decarboxylase. In SDS electrophoresis, tyrosine decarboxylase had the monomer molecular weight 75,000, showing a dimer structure for the enzyme.     

Affinity chromatography of tyrosine transfer RNAs.

Ricinus communis agglutinin, a lectin from castor beans has an affinity for β-d-galactose and tyrosine tRNAs of mammalian tissues have galactose in gal-Q base of their anticodons. We have studied interaction between tyrosine tRNAs and this lectin immobilized on solid supports using spacer arms of different lengths. Tyrosine tRNAs are separated from nineteen other tRNAs of bovine liver by affinity chromatography using the lectin immobilized to an agarose matrix. The results indicate that a spacer arm length of 10 Å between the agarose bead and the lectin gives the best separation. Two tyrosine tRNA isoacceptors are separated from each other and from other tRNAs in one step using this affinity column chromatography.     

Protein tyrosine phosphatase activity inLeishmania donovani

L. Donovani promastigotes were grown to late-log and 3-day stationary phase to determine the level of protein tyrosine phosphatase activity in crude extracts and in fractions following gel filtration column chromatography. Over 90% of the activity was soluble in a low salt extraction buffer in both phases of growth. Several peaks of activity were resolved following gel filtration of the crude extracts indicating that multiple tyrosine phosphatases are present in these cells. Tyrosine phosphatase activity was lower in 3-day stationary than in late log-phase cells and a reduction in the major peak of activity, eluting in a gel fraction corresponding to an M _r of approximately 168kDa, was observed.In vivo tyrosine phosphorylation was revealed by Western blot analysis. The degree of phosphorylation of at least two proteins differed in cells obtained from late log phase cultures as compared with 3-day stationary phase cultures. These observations indicate that changes in the balance between tyrosine phosphorylation and dephosphorylation occur with increasing culture age.Abbreviations MBP myelin basic protein - PMSF phenyl-methanesulfonylfluoride - PTP protein tyrosine phosphatase - RCML reduced, carboxyamidomethylated, maleylated lysozyme - YINAS Tyr-Ile-Asn-Ala-Ser     

Protein tyrosine phosphatase-1C is rapidly phosphorylated in tyrosine in macrophages in response to colony stimulating factor-1.

An approximately 64-kDa cytoplasmic protein is rapidly phosphorylated in tyrosine in the response of macrophages to colony stimulating factor-1. To identify this protein, BAC1.2F5 macrophages were incubated with or without colony stimulating factor-1, the phosphotyrosine-containing portion of their cytosolic fractions subjected to size exclusion chromatography, and the 45-70-kDa fraction further fractionated by reverse phase high pressure liquid chromatography (RP-HPLC). Tryptic peptides of pooled RP-HPLC fractions from stimulated cells (containing the approximately 64-kDa protein and an approximately 54-kDa protein) and from unstimulated cells (containing the approximately 54-kDa protein alone), were sequenced directly. All seven readable sequences of 8 sequenceable peptides present uniquely in the stimulated fraction were present in the sequence of the src homology 2 domain-containing protein tyrosine phosphatase-1C (PTP-1C). The identity of the approximately 64-kDa protein was confirmed by Western blotting with an antibody raised to a PTP-1C peptide. The rapid, growth factor-induced tyrosine phosphorylation of PTP-1C suggests that it may be involved in very early events in growth factor signal transduction.     

The hormonogenic tyrosine 5 of porcine thyroglobulin is sulfated

Our previous results showed that sulfated tyrosines of thyroglobulin (Tg), the molecular support of thyroid hormonosynthesis, are involved in the hormonogenic process. Moreover, the consensus sequence required for tyrosine sulfation is present in most of the hormonogenic sites. These observations suggest that tyrosine sulfation might play a critical role in the hormonogenic process. In this paper we studied the putative sulfation of tyrosine 5 contained in the preferential hormonogenic site. Porcine thyrocytes were cultured with thyrotropin but without iodide to preserve the sulfation state of tyrosine 5 and then incubated or not with [35S]sulfate. Secreted Tg was purified and submitted to peptide sequence analysis which confirmed the known peptide sequence of the NH(2) extremity of Tg:NIFEYQV. The treatment of [35S]sulfate-labeled Tg by leucine aminopeptidase, which sequentially digested its amino-terminal extremity, released the same amino acids and further analysis by thin layer chromatography showed that the tyrosine was sulfated. We concluded that tyrosine 5 is sulfated but the role of sulfate group in the hormonogenic process remains to be elucidated.     

Analysis of tyrosine and deuterium labelled tyrosine in tissues and body fluids

A gas chromatographic mass spectrometric method has been developed to determine tyrosine and deuterium labelled tyrosine in biological samples using alpha-methyltyrosine (alpha-Me Ty) or m-hydroxyphenylalanine as internal standards. With the latter standard both labelled and unlabelled tyrosine as well as alpha-Me Ty can be determined simultaneously, in for example human blood, following administration of alpha-Me Ty to inhibit catecholamine synthesis. After isolation of the amino acids on an ion exchange column (Amberlite IR 120) the butyl ester pentafluoropropionyl derivatives were prepared. In human plasma the precision of the method was determined at a level of 80 nmol tyrosine ml-1 and found to be +/- 5% (coefficient of variation, n = 10).     

Maize phenylalanine ammonia-lyase has tyrosine ammonia-lyase activity.

A full-length cDNA encoding phenylalanine ammonia-lyase (PAL) from Zea mays L. was isolated and the coding region was expressed in Escherichia coli as a C-terminal fusion to glutathione S-transferase. After purification by glutathione-Sepharose chromatography, the glutathione S-transferase moiety was cleaved off and the resulting PAL enzyme analyzed. In contrast to PAL from dicots, this maize PAL isozyme catalyzed the deamination of both L-phenylalanine (PAL activity) and L-tyrosine (tyrosine ammonia-lyase activity). These results provide unequivocal proof that PAL and tyrosine ammonia-lyase activities reside in the same polypeptide. In spite of large differences in the Michaelis constant and turnover number of the two activities, their catalytic efficiencies are very similar. Also, both activities have the same pH and temperature optima. These results imply that maize can produce p-coumaric acid from both phenylalanine and tyrosine.     

Determination of the tyrosine phosphorylation sites of the nicotinic acetylcholine receptor.

The peripheral nicotinic acetylcholine receptor (nAChR) is phosphorylated on tyrosine residues in vivo and in vitro at a high stoichiometry. We have previously reported that this tyrosine phosphorylation occurs on the beta, gamma, and delta subunits of the receptor and is implicated in both the modulation of the function of the receptor and localization of the receptor at the synapse. The specific tyrosine residue of each subunit which is phosphorylated is now identified. The endogenously phosphorylated nAChR from the electric organ of Torpedo californica was phosphorylated to maximal stoichiometry in vitro exclusively on tyrosine residues as indicated by phosphoamino acid analysis. Two-dimensional phosphopeptide maps of thermolysin limit digests of the isolated phosphorylated subunits indicated that each subunit is phosphorylated at a single site. To determine the site of tyrosine phosphorylation of the beta, gamma, and delta subunits, phosphorylated subunits were isolated and digested with trypsin. A single phosphotyrosine containing peptide from each subunit was purified by antiphosphotyrosine antibody affinity chromatography and reverse phase high performance liquid chromatography. The purified phosphopeptides were subjected to sequential Edman degradation and sequence analysis. Comparison of the phosphopeptide sequence data with the deduced amino acid sequence of each subunit indicated that Tyr-355 of beta, Tyr-364 of gamma, and Tyr-372 of delta are the sites of in vitro and in vivo tyrosine phosphorylation of the nAChR. Identification of these sites should facilitate further studies of the role of tyrosine phosphorylation in the regulation of receptor function.     

Identification of tyrosine O-sulfate in proteins by reverse-phase high-performance liquid chromatography: use of base hydrolysis combined with precolumn derivatization using phenyl isothiocyanate

A procedure has been developed for the analysis of tyrosine O-sulfate in proteins. Samples are subjected to base hydrolysis with Ba(OH)2, neutralized with sulfuric acid, and the majority of other amino acids removed by chromatography on Dowex AG 50 X 8. The average recovery of tyrosine O-sulfate from these procedures was 43%. Tyrosine O-sulfate was identified by reverse-phase HPLC as the phenylthiocarbamyl derivative following precolumn derivatization with phenyl isothiocyanate. The method has been applied to bovine fibrinogen giving a tyrosine O-sulfate content ranging from 0.59 to 1.23 mol/mol. These procedures were also shown to be suitable for the analysis of the incorporation of [35S]sulfate into tyrosine O-sulfate residues in proteins by intact cells.     

Organ specificity of glucocorticoid-sensitive tyrosine aminotransferase. Separation from aspartate aminotransferase isoenzymes

In order to study whether hormone-sensitive tyrosine aminotransferase exists in tissues other than liver, we have devised means to separate the liver-specific enzyme from other enzymes that transaminate tyrosine and to distinguish between the authentic enzyme and the principal "pseudotyrosine aminotransferases," which are the isoenzymes of aspartate aminotransferase. We accomplish this by suppressing proteolysis of the authentic enzyme using a buffer of pH 8.0 containing 0.1 M potassium chloride; enzyme extracted from liver in this buffer migrates as a single peak during chromatography on hydroxylapatite and represents the undegraded native form. A much smaller peak of tyrosine aminotransferase activity elutes at higher ionic strength and corresponds to a mixture of mitochondrial aspartate aminotransferase and partially degraded tyrosine aminotransferase. Cytosolic aspartate aminotransferase, in contrast, adsorbs weakly to the hydroxylapatite column and transaminates tyrosine very poorly although it readily utilizes monoiodotyrosine. The aspartate aminotransferase isoenzymes separate completely from tyrosine aminotransferase during chromatography on DEAE-Sepharose CL-6B. By combining these techniques with the use of specific antibodies, we show that brain, heart, and kidney do not contain tyrosine aminotransferase. Furthermore, we locate both isoenzymes of aspartate aminotransferase on polyacrylamide gels and show that both react histochemically as tyrosine aminotransferases when monoiodotyrosine is used as substrate. Use of these techniques, therefore, permits unambiguous identification of tyrosine aminotransferase and its separation from the background of nonspecific transamination.     

Purification and characterization of a protein tyrosine kinase from bovine spleen

Protein tyrosine kinase was purified extensively from a 30,000 X g particulate fraction of bovine spleen by a procedure involving four column chromatographies: DEAE-Sepharose, polyamino acids affinity, hydroxylapatite, and Sephacryl S-200 molecular sieving. The purification resulted in more than 3,000-fold enrichment in [Val5]angiotensin II phosphorylation activity (specific activity 202 nmol/min/mg). All column chromatography profiles showed single protein tyrosine kinase activity peaks with the exception of that of affinity chromatography, where about 50% of the enzyme activity appeared with the breakthrough fraction; only the bound enzyme was further purified. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of a purified sample phosphorylated in the presence of [gamma-32P]ATP revealed the presence of a single phosphorylated polypeptide of molecular weight 50,000 which represents about 40% of total protein. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions showed that protein tyrosine kinase activity co-migrated with the phosphoprotein. Stoichiometry of the phosphorylation of the 50-kDa polypeptide was found to be 1.0 mol/mol. The purified sample did not appear to contain phosphotyrosine protein phosphatase activity. Both casein and histone could be phosphorylated by the purified sample, and the phosphorylation occurred only at tyrosine residue, suggesting that there was no protein serine and threonine kinase contamination.     

Discriminating changes in protein structure using tyrosine conjugation

Chemical modification of proteins has been crucial in engineering protein‐based therapies, targeted biopharmaceutics, molecular probes, and biomaterials. Here, we explore the use of a conjugation‐based approach to sense alternative conformational states in proteins. Tyrosine has both hydrophobic and hydrophilic qualities, thus allowing it to be positioned at protein surfaces, or binding interfaces, or to be buried within a protein. Tyrosine can be conjugated with 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (PTAD). We hypothesized that individual protein conformations could be distinguished by labeling tyrosine residues in the protein with PTAD. We conjugated tyrosine residues in a well‐folded protein, bovine serum albumin (BSA), and quantified labeled tyrosine with liquid chromatography with tandem mass spectrometry. We applied this approach to alternative conformations of BSA produced in the presence of urea. The amount of PTAD labeling was found to relate to the depth of each tyrosine relative to the protein surface. This study demonstrates a new use of tyrosine conjugation using PTAD as an analytic tool able to distinguish the conformational states of a protein.     

A simplified procedure for the purification of rat liver tyrosine aminotransferase.

Rat liver tyrosine aminotransferase was purified by chromatography on CM-Sephadex C-50 and DEAE-cellulose, (NH4)2SO4 fractionation and gel filtration on Sephadex G-200. Livers from 400 rats can be easily worked up by this procedure. Furthermore, this purification method has the advantage that hepatic tryptophan 2,3-dioxygenase, which, like tyrosine aminotransferase, is induced by glucocorticosteroids, can be purified from the same homogenate. Tyrosine aminotransferase purified by this method was shown to be specific for 2-oxoglutarate. Its subunits have a molecular weight of 45 000. The following "apparent" Michaelis constants were determined: L-tyrosine, 1.7 X 10(-3) M; 2-oxoglutarate, 5.9 X 10(-4) M; and pyridoxal 5'-phosphate, 2.1 X 10(-6) M. Tyrosine aminotransferase, depleted of its cofactors, binds 4 molecules of pyridoxal 5'-phosphate per 90 000 daltons with a KA of 2.2 X 10(5) M-1.     

Zn(2+)-dependent tyrosine phosphorylation of a 68-kDa protein and its differentiation from Mg(2+)-dependent tyrosine phosphorylation in sheep platelets.

A 68-kDa protein that was tyrosine phosphorylated in the presence of Zn2+ and two proteins of 52 and 46 kDa that were tyrosine phosphorylated in the presence of Mg2+ were separated by column chromatography of a sheep platelet high speed supernatant on poly(Glu, Tyr)4:1 copolymer-Sepharose or tyrosine-Sepharose. Phosphorylation of the 68-kDa protein occurred maximally in the presence of Zn2+ while Mg2+ was ineffective. The kinases responsible for the Zn(2+)- and Mg(2+)-dependent tyrosine phosphorylation could also tyrosine phosphorylate poly(Glu, Tyr)4:1, histone, and angiotensin II with the same metal ion specificity. The two tyrosine kinase activities could be also distinguished by their differential response to polyamines and quercetin. Zn2+ stimulation did not appear to be due to the inhibition of a protein tyrosine phosphatase. Sephadex G-100 gel filtration of the fraction showing Zn(2+)-dependent tyrosine phosphorylation of the 68-kDa protein showed that the tyrosine kinase activity corresponded to a molecular mass of 68,000 and it showed a protein band of 68 kDa as detected by silver staining on sodium dodecyl sulfate-polyacrylamide gel.     

Highly sensitive assay for tyrosine hydroxylase activity by high-performance liquid chromatography

A highly sensitive assay for tyrosine hydroxylase (TH) activity by high-performance liquid chromatography (HPLC) with amperometric detection was devised based on the rapid isolation of enzymatically formed DOPA by a double-column procedure, the columns fitted together sequentially (the top column of Amberlite CG-50 and the bottom column of aluminium oxide). DOPA was adsorbed on the second aluminium oxide column, then eluted with 0.5 M hydrochloric acid, and assayed by HPLC with amperometric detection. d-Tyrosine was used for the control. α-Methyldopa was added to the incubation mixture as an internal standard after incubation. This assay was more sensitive than radioassays and 5 pmol of DOPA formed enzymatically could be measured in the presence of saturating concentrations of tyrosine and 6-methyltetrahydropterin. The TH activity in 2 mg of human putamen could be easily measured, and this method was found to be particularly suitable for the assay of TH activity in a small number of nuclei from animal and human brain.     

Functional characterization of peanut serine/threonine/tyrosine protein kinase: molecular docking and inhibition kinetics with tyrosine kinase inhibitors

Serine/threonine/tyrosine (STY) protein kinase from peanut is developmentally regulated and is induced by abiotic stresses. In addition, STY protein kinase activity is regulated by tyrosine phosphorylation. Kinetic mechanism of plant dual specificity protein kinases is not studied so far. Recombinant STY protein kinase occurs as a monomer in solution as shown by gel filtration chromatography. The relative phosphorylation rate of kinase against increasing enzyme concentrations follows a first-order kinetics indicating an intramolecular phosphorylation mechanism. Moreover, the active recombinant STY protein kinase could not transphosphorylate a kinase-deficient mutant of STY protein kinase. Molecular docking studies revealed that the tyrosine kinase inhibitors bind the protein kinase at the same region as ATP. STY protein kinase activity was inhibited by the tyrosine kinase inhibitors, and the inhibitor potency series against the recombinant STY protein kinase was tyrphostin > genistein > staurosporine. The inhibition constant (K(i)), and the IC(50) value of STY protein kinase for tyrosine kinase inhibitors with ATP and histone are discussed. All the inhibitors competed with ATP. Genistein was an uncompetitive inhibitor with histone, whereas staurosporine and tyrphostin were linear mixed type noncompetitive inhibitors with histone. Molecular docking and kinetic analysis revealed that Y148F mutant of the "ATP-binding loop" and Y297F mutant of the "activation loop" showed a dramatic increase in K(i) values for genistein and tyrphostin with respect to wild-type STY protein kinase. Data presented here provide the direct evidence on the mechanism of inhibition of plant protein kinases by tyrosine kinase inhibitors. This study also suggests that tyrosine kinase inhibitors may be useful in unraveling the plant tyrosine phosphorylation signaling cascades.     

An improved micromethod for tyrosine estimation

A modified and improved micromethod for tyrosine determination has been developed. The method is sensitive, economic and applicable for estimation of tyrosine released in enzymatic reactions and in tissue. A range of Folin-Ciocalteu (FC) reagent was used to optimize the conditions for the development of blue color. Thus in 1.5 ml of the assay system, the suitably diluted FC reagent at the final concentration of 0.2 N gave a rapid optimum color development with an absorption maximum at 750 nm. Color development showed a linear relationship in the range of 2 to 16 microg tyrosine for a described assay system under optimized conditions. Thus, the method is 3-fold more sensitive in terms of its estimation range than a conventional method. The blue color formed was stable up to 24 h. The applicability of the method for tyrosine determination in the assay of lysosomal cathepsin D and in tissue was checked by comparison to the conventional procedure. Under both systems the results obtained by the micromethod were identical to those obtained by the conventional method. In general the method that produces quantitatively a blue color, not only is rapid and economical in terms of chemical usage but also has application for routine biochemical analysis.     

Interactions of the human red cell membrane tyrosine kinase with heparin

Heparin interacts with protein kinases in various ways; the different patterns of behavior of heparin towards protein kinases contributes to the characterization of these enzymes. We studied the interactions between heparin and a new type of tyrosine kinase extracted from the normal human red cell membrane. We found that heparin inhibited kinase activity by competition with ATP. Furthermore the interaction of heparin with the red cell membrane tyrosine kinase allowed us to use heparin-agarose chromatography as a step towards tyrosine kinase purification.     

OH radical-induced products of tyrosine peptides

Reactions of radiation-generated OH radicals with tyrosine and its homopeptides, i.e. L-Tyr-L-Tyr and L-Tyr-L-Tyr-L-Tyr, in N2O saturated solutions were shown to give crosslinks between the peptide chains with high yields. High-performance liquid chromatography, capillary gas chromatography and mass spectrometry were used for isolation and identification of the monomeric and dimeric products. Evidence is presented for the crosslinking to occur through C-C and C-O-C bonds. To the best of our knowledge, the formation of the ether type of crosslink is demonstrated for the first time. Mechanisms of product formation are also discussed, which involve radicals that were described in previous pulse radiolysis studies.