scholarly journals The binding of the coenzyme pyridoxal 5'-phosphate and analogues of the substrate-coenzyme complex to tyrosine decarboxylase

1980 ◽  
Vol 185 (1) ◽  
pp. 41-46 ◽  
Author(s):  
A Orlacchio ◽  
C Borri-Voltattorni ◽  
C Turano
Keyword(s):  
Active Site ◽  
Tyrosine Aminotransferase ◽  
Phosphate Group ◽  
Significant Fraction ◽  
Tyrosine Decarboxylase ◽  
Binding Process ◽  
Substrate Analogues ◽  
Great Affinity ◽  
Correct Alignment ◽  
Aldehydic Group

Phosphopyridoxyl derivatives, which are stable analogues of a substrate-coenzyme complex, are bound at the active site with great affinity. From a comparison of the interaction of a number of such compounds with the apoenzyme the delta G0 values for the binding of the substrate carboxy and phenyl groups and of the coenzyme aldehydic group were determined to be equal to (or more negative than) ‒3.8. ‒8.4 and ‒12.5kJ/mol (-0.9, ‒1.9 and ‒3kcal/mol) respectively; the delta G0 for the binding of the coenzyme phosphate group was shown to be more negative than ‒20.5kJ/mol (-4.9kcal/mol). Two features of the binding process of the coenzyme-substrate analogues to tyrosine decarboxylase have already been found in the case of tyrosine aminotransferase [Borri-Voltattorni, Orlacchio, Giartosio, Conti & Turano (1975) Eur. J. Biochem. 53, 151-160]: (1) in the binding of the substrate to the enzyme a significant fraction of the instrinsic delta G0 appears to be used for some associated endoergonic process; (2) the delta H0 and delta S0 of binding appear to be very sensitive indicators of the correct alignment of the substrate-coenzyme and analogues at the active site.

scholarly journals Probing the ionization state of substrate α-d-glucopyranosyl phosphate bound to glycogen phosphorylase b

1995 ◽  
Vol 308 (3) ◽  
pp. 1017-1023 ◽  
Author(s):  
I P Street ◽  
S G Withers
Keyword(s):  
Active Site ◽  
Glycogen Phosphorylase ◽  
Ph Dependence ◽  
Substrate Inhibition ◽  
19F Nmr ◽  
Ionization State ◽  
Nmr Studies ◽  
Substrate Analogues ◽  
Glycogen Phosphorylase B ◽  
Pka Value

The ionization state of the substrate alpha-D-glucopyranosyl phosphate bound at the active site of glycogen phosphorylase has been probed by a number of techniques. Values of Ki determined for a series of substrate analogue inhibitors in which the phosphate moiety bears differing charges suggest that the enzyme will bind both the monoanionic and dianionic substrates with approximately equal affinity. These results are strongly supported by 31P- and 19F-NMR studies of the bound substrate analogues alpha-D-glucopyranosyl 1-methylenephosphonate and 2-deoxy-2-fluoro-alpha-D-glucopyranosyl phosphate, which also suggest that the substrate can be bound in either ionization state. The pH-dependences of the inhibition constants K1 for these two analogues, which have substantially different phosphate pK2 values (7.3 and 5.9 respectively), are found to be essentially identical with the pH-dependence of K(m) values for the substrate, inhibition decreasing according to an apparent pKa value of 7.2. This again indicates that there is no specificity for monoanion or dianion binding and also reveals that binding is associated with the uptake of a proton. As the bound substrate is not protonated, this proton must be taken up by the proton.

scholarly journals The Mechanism of the Tyrosine Transporter TyrP Supports a Proton Motive Tyrosine Decarboxylation Pathway in Lactobacillus brevis

2006 ◽  
Vol 188 (6) ◽  
pp. 2198-2206 ◽  
Author(s):  
Wout A. M. Wolken ◽  
Patrick M. Lucas ◽  
Aline Lonvaud-Funel ◽  
Juke S. Lolkema
Keyword(s):  
Phenyl Ring ◽  
Lactobacillus Brevis ◽  
Proton Motive Force ◽  
Proton Pumping ◽  
Hydroxyl Group ◽  
Transporter Gene ◽  
Tyrosine Decarboxylase ◽  
Rate Analysis ◽  
Substrate Analogues ◽  
Decarboxylation Reaction

ABSTRACT The tyrosine decarboxylase operon of Lactobacillus brevis IOEB9809 contains, adjacent to the tyrosine decarboxylase gene, a gene for TyrP, a putative tyrosine transporter. The two genes potentially form a proton motive tyrosine decarboxylation pathway. The putative tyrosine transporter gene of L. brevis was expressed in Lactococcus lactis and functionally characterized using right-side-out membranes. The transporter very efficiently catalyzes homologous tyrosine-tyrosine exchange and heterologous exchange between tyrosine and its decarboxylation product tyramine. Tyrosine-tyramine exchange was shown to be electrogenic. In addition to the exchange mode, the transporter catalyzes tyrosine uniport but at a much lower rate. Analysis of the substrate specificity of the transporter by use of a set of 19 different tyrosine substrate analogues showed that the main interactions between the protein and the substrates involve the amino group and the phenyl ring with the para hydroxyl group. The carboxylate group that is removed in the decarboxylation reaction does not seem to contribute to the affinity of the protein for the substrates significantly. The properties of the TyrP protein are those typical for precursor-product exchangers that operate in proton motive decarboxylation pathways. It is proposed that tyrosine decarboxylation in L. brevis results in proton motive force generation by an indirect proton pumping mechanism.

scholarly journals Insights into the phosphoryl transfer catalyzed by cAMP-dependent protein kinase

2014 ◽  
Vol 70 (a1) ◽  
pp. C449-C449
Author(s):  
Oksana Gerlits ◽  
Amit Das ◽  
Jianhui Tian ◽  
Malik Keshwani ◽  
Susan Taylor ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinases ◽  
Active Site ◽  
Phosphate Group ◽  
Nucleoside Triphosphate ◽  
Phosphoryl Transfer ◽  
Hydrogen Atoms ◽  
Dependent Protein Kinase ◽  
Camp Dependent Protein Kinase ◽  
Dependent Protein

Protein kinases are involved in a number of cell signaling pathways. They catalyze phosphorylation of proteins and regulate the majority of cellular processes (such as growth, differentiation, lipid metabolism, regulation of sugar, nucleic acid synthesis, etc.). Chemically, protein kinases covalently transfer the gamma-phosphate group of a nucleoside triphosphate (e.g. ATP) to a hydroxyl group of a Ser, Thr or Tyr residue of substrate protein or peptide. The reaction involves moving hydrogen atoms between the enzyme, substrate and nucleoside. The unanswered question is whether the proton transfer from the Ser residue happens before the phosphoryl transfer using the general acid-base catalyst, Asp166, or after the reaction went through the transition state by directly protonating the phosphate group. To address this key question about the phosphoryl transfer, we determined a number of X-ray structures of ternary complexes of catalytic subunit of cAMP-dependent protein kinase (PKAc) with various substrates, nucleotides and cofactors. Importantly, we were able to trap and mimic the initial (Michaelis complex) and final (product complex) stages of the reaction. The results demonstrate that Mg2+, Ca2+, Sr2+, and Ba2+ metal ions bind to the active site and facilitate the reaction to produce ADP and a phosphorylated peptide. The study also revealed that metal-free PKAc can facilitate the phosphoryl transfer reaction; a result that was confirmed with single turnover enzyme kinetics measurements. Comparison of the product and the pseudo-Michaelis complex structures, in conjunction with molecular dynamics simulations, reveals conformational, coordination, and hydrogen bonding changes that help further our understanding of the mechanism, roles of metals, and active site residues involved in PKAc activity.

Difference in Conformation of Virginiamycin M1 in Chloroform and Bound Form in the 50S Ribosome or Streptogramin Acetyltransferase

2004 ◽  
Vol 57 (5) ◽  
pp. 415 ◽  
Author(s):  
Jason Dang ◽  
B. Mikael Bergdahl ◽  
Frances Separovic ◽  
Robert T. C. Brownlee ◽  
Robert P. Metzger
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Active Site ◽  
Major Change ◽  
X Ray ◽  
Binding Process ◽  
High Resolution Nmr ◽  
Virginiamycin M1

The conformation of virginiamycin M1 (VM1) in chloroform, determined by high-resolution NMR experiments, differs significantly from that of the X-ray crystal structure of VM1 bound to the 50S ribosome and to the active site of a streptogramin acetyltransferase enzyme. This implies that the binding process to these entities causes a major change in VM1 conformation.

scholarly journals Modification of pig heart lactate dehydrogenase with methyl methanethiosulphonate to produce an enzyme with altered catalytic activity

1977 ◽  
Vol 161 (3) ◽  
pp. 643-651 ◽  
Author(s):  
D P Bloxham ◽  
D C Wilton
Keyword(s):  
Lactate Dehydrogenase ◽  
Active Site ◽  
Thiol Group ◽  
Dilute Solution ◽  
Substrate Analogues ◽  
Steady State Kinetics ◽  
Active Methyl ◽  
Catalytically Active ◽  
Modified Enzyme ◽  
Formation Of Complexes

Methyl methanethiosulphonate was used to produce a modification of the essential thiol group in lactate dehydrogenase which leaves the enzyme catalytically active. Methyl methanethiosulphonate produced a progressive inhibition of enzyme activity, with 2mM-pyruvate and 0.14mM-NADH as substrates, which ceased once the enzyme had lost 70-90% of its activity. In contrast, with 10mM-lactate and 0.4mM-NAD+ as substrates the enzyme was virtually completely inhibited. The observed inhibition was critically dependent on the chosen substrate concentration, since methanethiolation with methyl methanethiosulphonate resulted in a large decrease in affinity for pyruvate. At 0.14mM-NADH, methanethiolation increased the apparent KmPyr from from 40micronM for the control enzyme to 12mM for the modified enzyme. Steady-state kinetics showed that there was not a statistically significant change in either KmNADH or KsNADH. At saturating NADH and pyruvate concentrations, the Vmax. was virtually unaffected for the methanethiolated enzyme. However, a decrease in Vmax. was observed when the modified enzyme was incubated in dilute solution. The modification of lactate dehydrogenase by methyl methanethiosulphonate involved the active site, since inhibition was completely prevented by substrate-analogue pairs such as NADH and oxamate or NAD+ and oxalate. The formation of complexes between methanethiolated lactate dehydrogenase and substrates or substrate analogues can also be shown by re-activation experiments. The methanethiolated enzyme was re-activated in a time-dependent reaction by dithiothreitol and this was prevented by oxamate, by NADH and by NADH plus oxamate in increasing order of effectiveness. The results of this work are interpreted in terms of a role for the essential thiol group in the binding of substrates.

scholarly journals GMP and IMP Are Competitive Inhibitors of CMY-10, an Extended-Spectrum Class C β-Lactamase

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Jung-Hyun Na ◽  
Young Jun An ◽  
Sun-Shin Cha
Keyword(s):  
Crystal Structure ◽  
Active Site ◽  
Binding Mode ◽  
Competitive Inhibitor ◽  
Phosphate Group ◽  
The Other ◽  
Extended Spectrum ◽  
Competitive Inhibitors ◽  
Class C

ABSTRACT Nucleotides were effective in inhibiting the class C β-lactamase CMY-10. IMP was the most potent competitive inhibitor, with a Ki value of 16.2 μM. The crystal structure of CMY-10 complexed with GMP or IMP revealed that nucleotides fit into the R2 subsite of the active site with a unique vertical binding mode where the phosphate group at one terminus is deeply bound in the subsite and the base at the other terminus faces the solvent.

scholarly journals Tyrosine Aminotransferase Catalyzes the Final Step of Methionine Recycling in Klebsiella pneumoniae

1999 ◽  
Vol 181 (6) ◽  
pp. 1739-1747 ◽  
Author(s):  
Jacqueline Heilbronn ◽  
Judith Wilson ◽  
Bradley J. Berger
Keyword(s):  
Amino Acid ◽  
Klebsiella Pneumoniae ◽  
Amino Acid Sequence ◽  
Paracoccus Denitrificans ◽  
Rhizobium Meliloti ◽  
Aromatic Amino Acids ◽  
Tyrosine Aminotransferase ◽  
E Coli ◽  
Substrate Analogues ◽  
Terminal Amino

ABSTRACT An aminotransferase which catalyzes the final step in methionine recycling from methylthioadenosine, the conversion of α-ketomethiobutyrate to methionine, has been purified fromKlebsiella pneumoniae and characterized. The enzyme was found to be a homodimer of 45-kDa subunits, and it catalyzed methionine formation primarily using aromatic amino acids and glutamate as the amino donors. Histidine, leucine, asparagine, and arginine were also functional amino donors but to a lesser extent. The N-terminal amino acid sequence of the enzyme was determined and found to be almost identical to the N-terminal sequence of both the Escherichia coli and Salmonella typhimurium tyrosine aminotransferases (tyrB gene products). The structural gene for the tyrosine aminotransferase was cloned from K. pneumoniae and expressed in E. coli. The deduced amino acid sequence displayed 83, 80, 38, and 34% identity to the tyrosine aminotransferases from E. coli, S. typhimurium, Paracoccus denitrificans, andRhizobium meliloti, respectively, but it showed less than 13% identity to any characterized eukaryotic tyrosine aminotransferase. Structural motifs around key invariant residues placed the K. pneumoniae enzyme within the Ia subfamily of aminotransferases. Kinetic analysis of the aminotransferase showed that reactions of an aromatic amino acid with α-ketomethiobutyrate and of glutamate with α-ketomethiobutyrate proceed as favorably as the well-known reactions of tyrosine with α-ketoglutarate and tyrosine with oxaloacetate normally associated with tyrosine aminotransferases. The aminotransferase was inhibited by the aminooxy compounds canaline and carboxymethoxylamine but not by substrate analogues, such as nitrotyrosine or nitrophenylalanine.

scholarly journals Determination of the Substrate Binding Mode to the Active Site Iron of (S)-2-Hydroxypropylphosphonic Acid Epoxidase Using17O-Enriched Substrates and Substrate Analogues†

Biochemistry ◽  
2007 ◽  
Vol 46 (44) ◽  
pp. 12628-12638 ◽  
Author(s):  
Feng Yan ◽  
Sung-Ju Moon ◽  
Pinghua Liu ◽  
Zongbao Zhao ◽  
John D. Lipscomb ◽  
...  
Keyword(s):  
Active Site ◽  
Substrate Binding ◽  
Binding Mode ◽  
Substrate Analogues

scholarly journals Steady-state kinetics and inhibition of anaerobically purified human homogentisate 1,2-dioxygenase

2005 ◽  
Vol 386 (2) ◽  
pp. 305-314 ◽  
Author(s):  
Edwin J. A. VELDHUIZEN ◽  
Frédéric H. VAILLANCOURT ◽  
Cheryl J. WHITING ◽  
Marvin M.-Y. HSIAO ◽  
Geneviève GINGRAS ◽  
...  
Keyword(s):  
Steady State ◽  
Active Site ◽  
Ternary Complex ◽  
Specific Activity ◽  
Complex Mechanism ◽  
Substrate Analogues ◽  
Steady State Kinetics ◽  
Km Value ◽  
Substrate Concentrations ◽  
Active Preparation

HGO (homogentisate 1,2-dioxygenase; EC 1.13.11.5) catalyses the O2-dependent cleavage of HGA (homogentisate) to maleylacetoacetate in the catabolism of tyrosine. Anaerobic purification of heterologously expressed Fe(II)-containing human HGO yielded an enzyme preparation with a specific activity of 28.3± 0.6 μmol·min−1·mg−1 (20 mM Mes, 80 mM NaCl, pH 6.2, 25 °C), which is almost twice that of the most active preparation described to date. Moreover, the addition of reducing agents or other additives did not increase the specific activity, in contrast with previous reports. The apparent specificity of HGO for HGA was highest at pH 6.2 and the steady-state cleavage of HGA fit a compulsory-order ternary-complex mechanism (Km value of 28.6±6.2 μM for HGA, Km value of 1240±160 μM for O2). Free HGO was subject to inactivation in the presence of O2 and during the steady-state cleavage of HGA. Both cases involved the oxidation of the active site Fe(II). 3-Cl HGA, a potential inhibitor of HGO, and its isosteric analogue, 3-Me HGO, were synthesized. At saturating substrate concentrations, HGO cleaved 3-Me and 3-Cl HGA 10 and 100 times slower than HGA respectively. The apparent specificity of HGO for HGA was approx. two orders of magnitude higher than for either 3-Me or 3-Cl HGA. Interestingly, 3-Cl HGA inactivated HGO only twice as rapidly as HGA. This contrasts with what has been observed in mechanistically related dioxygenases, which are rapidly inactivated by chlorinated substrate analogues, such as 3-hydroxyanthranilate dioxygenase by 4-Cl 3-hydroxyanthranilate.

scholarly journals Combined QM/MM calculations of active-site vibrations in binding process of P450cam to putidaredoxin

2008 ◽  
Vol 102 (3) ◽  
pp. 427-432 ◽  
Author(s):  
Marek Freindorf ◽  
Yihan Shao ◽  
Jing Kong ◽  
Thomas R. Furlani
Keyword(s):  
Active Site ◽  
Binding Process
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