scholarly journals Evidence for the importance of arginine residues in pig kidney alkaline phosphatase

1979 ◽  
Vol 181 (1) ◽  
pp. 137-142 ◽  
Author(s):  
M N Woodroofe ◽  
P J Butterworth
Keyword(s):  
Alkaline Phosphatase ◽  
Active Site ◽  
Competitive Inhibitor ◽  
Arginine Residue ◽  
Pig Kidney ◽  
Close Proximity ◽  
Arginine Residues ◽  
Km Value ◽  
Uncompetitive Inhibitor ◽  
Kidney Alkaline Phosphatase

The arginine-specific reagents 2,3-butanedione and phenylglyoxal inactivate pig kidney alkaline phosphatase. As inactivation proceeds there is a progressive fall in Vmax. of the enzyme, but no demonstrable change in the Km value for substrate. Pi, a competitive inhibitor, and AMP, a substrate of the enzyme, protect alkaline phosphatase against the arginine-specific reagents. These effects are explicable by the assumption that the enzyme contains an essential arginine residue at the active site. Protection is also afforded by the uncompetitive inhibitor NADH through a partially competive action against the reagents. Enzyme that has been exposed to the reagents has a decreased sensitivity to NADH inhibition. It is suggested that an arginine residue is important for NADH binding also, although this residue is distinct from that at the catalytic site. The protection given by NADH against loss of activity is indicative of the close proximity of the active and NADH sites.

scholarly journals Modification of an arginine residue in pig kidney general acyl-coenzyme A dehydrogenase by cyclohexane-1,2-dione

1982 ◽  
Vol 207 (3) ◽  
pp. 415-419 ◽  
Author(s):  
Z Y Jiang ◽  
C Thorpe
Keyword(s):  
Residual Activity ◽  
Competitive Inhibitor ◽  
Borate Buffer ◽  
Arginine Residue ◽  
Pig Kidney ◽  
Excess Substrate ◽  
Arginine Residues ◽  
Modified Enzyme ◽  
High Concentrations ◽  
Acyl Coenzyme A

The flavoenzyme pig kidney general acyl-CoA dehydrogenase (EC 1.3.99.3) is inactivated by cyclohexane-1,2-dione in borate buffer in a reaction that exhibits pseudo-first-order kinetics. Strong protection is afforded by the substrate octanoyl-CoA, as well as by heptadecyl-CoA, a potent competitive inhibitor of the dehydrogenase that does not reduce enzyme flavin. Enzyme exhibiting 10% residual activity in borate buffer contains about 1.3 modified arginine residues per flavin molecule. Very little reduction of the modified enzyme in borate buffer occurs at high concentrations of octanoyl-CoA, in marked contrast with the stoicheiometric reduction of the native enzyme. However, in phosphate buffer alone, the modified enzyme exhibits 55% residual activity and, although binding of substrate is still seriously impaired (apparent Kd=14 microM), excess substrate effects the formation of the characteristic reduced flavin X enoyl-CoA charge-transfer complex. These results suggest that the susceptible arginine residue, though not catalytically essential, is probably within the acyl-CoA-binding site of general acyl-CoA dehydrogenase.

Identification of Functional Groups of Pig Kidney Alkaline Phosphatase by Specific Inhibitors

1975 ◽  
Vol 30 (11-12) ◽  
pp. 829-831 ◽  
Author(s):  
Jan Ahlers
Keyword(s):  
Alkaline Phosphatase ◽  
Functional Groups ◽  
Pig Kidney ◽  
Kidney Alkaline Phosphatase ◽  
Specific Inhibitors ◽  
Regulatory Sites

Abstract Inactivation studies with 17 group-specific inhibitors showed that amino, hystidyl and tyrosyl residues probably are components of the active and/or regulatory sites of pig kidney alkaline phosphatase.

scholarly journals Role of Arginines in Coenzyme A Binding and Catalysis by the Phosphotransacetylase from Methanosarcina thermophila

2001 ◽  
Vol 183 (14) ◽  
pp. 4244-4250 ◽  
Author(s):  
Prabha P. Iyer ◽  
James G. Ferry
Keyword(s):  
Active Site ◽  
Coenzyme A ◽  
Sulfhydryl Group ◽  
Salt Bridge ◽  
Competitive Inhibitor ◽  
Enzyme Inactivation ◽  
Methanosarcina Thermophila ◽  
Arginine Residues ◽  
Substrate Protection

ABSTRACT Phosphotransacetylase (EC 2.3.1.8 ) catalyzes the reversible transfer of the acetyl group from acetyl phosphate to coenzyme A (CoA): CH3COOPO3 2− + CoASH ⇆ CH3COSCoA + HPO4 2−. The role of arginine residues was investigated for the phosphotransacetylase from Methanosarcina thermophila. Kinetic analysis of a suite of variants indicated that Arg 87 and Arg 133 interact with the substrate CoA. Arg 87 variants were reduced in the ability to discriminate between CoA and the CoA analog 3′-dephospho-CoA, indicating that Arg 87 forms a salt bridge with the 3′-phosphate of CoA. Arg 133 is postulated to interact with the 5′-phosphate of CoA. Large decreases in k cat andk cat/Km for all of the Arg 87 and Arg 133 variants indicated that these residues are also important, although not essential, for catalysis. Large decreases ink cat andk cat/Km were also observed for the variants in which lysine replaced Arg 87 and Arg 133, suggesting that the bidentate interaction of these residues with CoA or their greater bulk is important for optimal activity. Desulfo-CoA is a strong competitive inhibitor of the enzyme, suggesting that the sulfhydryl group of CoA is important for the optimization of CoA-binding energy but not for tight substrate binding. Chemical modification of the wild-type enzyme by 2,3-butanedione and substrate protection by CoA indicated that at least one reactive arginine is in the active site and is important for activity. The inhibition pattern of the R87Q variant indicated that Arg 87 is modified, which contributes to the inactivation; however, at least one additional active-site arginine is modified leading to enzyme inactivation, albeit at a lower rate.

scholarly journals The reversible inactivation of pig kidney alkaline phosphatase at low pH

1968 ◽  
Vol 108 (2) ◽  
pp. 243-246 ◽  
Author(s):  
P. J. Butterworth
Keyword(s):  
Alkaline Phosphatase ◽  
Acid Treatment ◽  
Gel Filtration ◽  
Reversible Inactivation ◽  
Pig Kidney ◽  
Reactivation Mechanism ◽  
Increasing Temperature ◽  
Filtration Properties ◽  
Kinetics Of ◽  
Kidney Alkaline Phosphatase

1. Pig kidney alkaline phosphatase is inactivated by treatment with acid at 0°. 2. Inactivated enzyme can be partially reactivated by incubation at 30° in neutral or alkaline buffer. The amount of reactivation that occurs depends on the degree of acid treatment; enzyme that has been inactivated below pH3·3 shows very little reactivation. 3. Studies of the kinetics of reactivation indicate that the process is greatly accelerated by increasing temperature and proceeds by a unimolecular mechanism. The reactivated enzyme has electrophoretic and gel-filtration properties identical with those of non-treated enzyme. 4. The results can be best explained by assuming that a lowering of the pH causes a reversible conformational change of the alkaline phosphatase molecule to a form that is no longer enzymically active but is very susceptible to permanent denaturation by prolonged acid treatment. A reactivation mechanism involving sub-unit recombination seems unlikely.

An essential arginine residue in the active-site pocket of glycogen phosphorylase

1977 ◽  
Vol 55 (4) ◽  
pp. 465-473 ◽  
Author(s):  
E. C. Y. Li ◽  
R. J. Fletterick ◽  
J. Sygusch ◽  
N. B. Madsen
Keyword(s):  
Amino Acid ◽  
Electron Density ◽  
Active Site ◽  
Protein Molecule ◽  
Competitive Inhibitor ◽  
Arginine Residue ◽  
Sodium Borate ◽  
Appreciable Effect ◽  
First Order ◽  
Active Site Pocket

Phosphorylases a and b (EC 2.4.1.1) were inactivated by selective modification of arginyl residues on reaction with 2,3-butanedione in sodium borate buffer. The rate of inactivation was slightly greater for phosphorylase a than b. The course of inactivation followed pseudo-first-order kinetics with some deviations at low rates or at more than 60% inactivation. The rate of inactivation was first order with respect to butanedione concentration. The inactivation was partially reversible, and ultracentrifugal studies showed no change in subunit association or dissociation. Amino acid analyses indicated that several arginines were modified during inactivation and that no other amino acid was affected. Protection from inactivation was provided by the substrate glucose 1-phosphate (G1P), alone or together with the allosteric activator AMP, as well as by the competitive inhibitor UDP-glucose. The rate of inactivation of phosphorylase b was also retarded by the presence of AMP alone. Glycogen did not have any appreciable effect on inactivation. The Km of G1P for phosphorylase a remained constant over the course of inactivation, while the Km values of G1P and AMP for phosphorylase b increased. The modification of cross-linked tetragonal microcrystals of phosphorylase a followed the same trend as the enzyme in solution, although the rate of inactivation was slower. The X-ray crystallography studies at 6 Å (1 Å = 0.1 nm) resolution, of butanedione-treated cross-linked tetragonal crystals of phosphorylase a showed a large new peak of electron density at the end of a long side chain in the active-site pocket. The substrates G1P and arsenate, as well as UDP-glucose, had previously been shown to bind in that location. Other, small peaks of electron density were found in locations on the outside of the protein molecule. UDP-glucose failed to bind to the active site of crystals which had been treated with butanedione, while AMP, which also binds in the active-site pocket, showed a lower occupancy. This work indicates the presence of a functional arginine residue at the binding site for G1P in glycogen phosphorylases a and b.

scholarly journals Nucleoside pyrophosphatase activity associated with pig kidney alkaline phosphatase

1971 ◽  
Vol 124 (5) ◽  
pp. 891-896 ◽  
Author(s):  
Milica Wass ◽  
P. J. Butterworth
Keyword(s):  
Alkaline Phosphatase ◽  
Pig Kidney ◽  
Bivalent Cations ◽  
Free Nucleotides ◽  
Pyrophosphatase Activity ◽  
Kidney Alkaline Phosphatase

1. A study was made of the hydrolysis, at pH9.0, of ATP and ADP catalysed by pig kidney alkaline phosphatase. Both of these nucleoside pyrophosphates are substrates for the enzyme; Km values are 4×10-5m for ATP and 6.3×10-5m for ADP. Vmax. for ADP is approximately double that of ATP. 2. Above 0.1mm approximately, both ATP and ADP are inhibitory, but the inhibition is reversible by the addition of Mg2+ ions to form MgATP2- or MgADP- complexes. The complexes, besides being non-inhibitory, are also substrates for the enzyme with Km values identical with those of the respective free nucleotides. 3. Mg2+ ions are inhibitory when present in excess of ATP or ADP. The degree of inhibition is greater with ATP as substrate, but with both ATP and ADP a mixed competitive–non-competitive type of inhibition is observed. 4. It is suggested that under normal conditions the enzyme is inhibited by cellular concentrations of ATP plus ADP but that an increase in the concentration of Mg2+ ions stimulates activity by relieving nucleoside pyrophosphate inhibition. The properties may be of importance in the regulation of the transport of bivalent cations.

scholarly journals Modification of myo-inositol monophosphatase by the arginine-specific reagent phenylglyoxal

1989 ◽  
Vol 264 (2) ◽  
pp. 419-422 ◽  
Author(s):  
R G Jackson ◽  
N S Gee ◽  
C I Ragan
Keyword(s):  
Protective Effect ◽  
Competitive Inhibitor ◽  
Small Degree ◽  
Arginine Residue ◽  
Inositol Monophosphatase ◽  
Degree Of Protection ◽  
Uncompetitive Inhibitor ◽  
Enzyme Intermediate ◽  
Specific Reagent

myo-Inositol monophosphatase is inhibited by the arginine-specific reagent phenylglyoxal. The rate of inactivation is decreased in the presence of Pi, a competitive inhibitor of the enzyme. The effect of Pi is dependent on the presence of Mg2+, but is unaffected by Li+, an uncompetitive inhibitor. In the absence of Mg2+, the substrate, Ins(1)P, binds to the enzyme but is not converted into products, and affords only a small degree of protection against inactivation by phenylglyoxal. Li+ had no further effect under these conditions, but in the presence of Mg2+ caused a marked potentiation of the protective effect of substrate alone. In the absence of substrate, Li+ had no effect on activation by phenylglyoxal. Incorporation of 14C-labelled phenylglyoxal showed that inactivation was associated with modification of a single arginine residue per monomer in the dimeric enzyme. These findings support a mechanism in which Li+ inhibits monophosphatase by trapping a phosphorylated enzyme intermediate and preventing its hydrolysis.

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