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PubMed1994

Beta-ureidopropionase with N-carbamoyl-alpha-L-amino acid amidohydrolase activity from an aerobic bacterium, Pseudomonas putida IFO 12996.

beta-Ureidopropionase of aerobic bacterial origin was purified to homogeneity from Pseudomonas putida IFO 12996. The enzyme shows a broad substrate specificity. In addition to beta-ureidopropionate (Km 3.74 mM, Vmax 4.12 U/mg), gamma-ureido-n-butyrate (Km 11.6 mM, Vmax 19.4 U/mg), and several N-carbamoyl-alpha-amino acids, such as N-carbamoylglycine (Km 0.68 mM, Vmax 9.14 x 10(-2) U/mg), N-carbamoyl-L-alanine (Km 1.56 mM, Vmax 1.00 U/mg), N-carbamoyl-L-serine (Km 75.1 mM, Vmax 3.78 U/mg), and N-carbamoyl-DL-alpha-amino-n-butyrate (Km 2.81 mM, Vmax 1.08 U/mg), are also hydrolyzed. The hydrolysis of N-carbamoyl-alpha-amino acids is strictly L enantiomer specific. N-Formyl-L-alanine and N-acetyl-L-alanine are also hydrolyzed by the enzyme, but the rate of hydrolysis is lower than the rate for N-carbamoyl-L-alanine. The enzyme requires a divalent metal ion, such as Co2+, Ni2+ or Mn2+, for activity, and is significantly affected by sulfhydryl reagents. The enzyme consists of two polypeptide chains with identical relative molecular mass M(r) 45000. The broad substrate specificity and metal ion dependence of the enzyme show that the beta-ureidopropionase of this aerobic bacterium is quite different from the beta-ureidopropionases of mammals and anaerobic bacteria.

Amidohydrolases↗
PubMedDate not supplied

Studies on the Zn2+/Co2+ exchange with acylamino acid amidohydrolase from pig kidney.

The kinetics of inactivation of the Zn2+-metalloenzyme acyl-amino acid amido hydrolase by chelating ligands were studied. The rate of inactivation by 1,10-phenanthroline is enhanced by histidine and inhibited in the presence of phenyl-alanine. Removal of the metal ion increases the heat stability and decreases the pH stability of the enzyme. Reactivation of the inactive metal free enzyme is possible with Zn2+ and Co2+. Titration of the metal free protein with a free enzyme is possible with Zn2+ and Co2+. Titration of the metal free protein with a Co2+/nitrilotriacetate metal buffer revealed a dissociation constant of about 10(-7) M for the Co2+ enzyme (Zn2+ enzyme = 10(-10) M). The Co2+ substituted enzyme is less stable than the Zn2+ enzyme. Histidine and phenylalanine protect the Co2+ enzyme against inactivation by 1,10-phenanthroline.

Amidohydrolases↗
PubMed1988

Structures of amidohydrolases. Amino acid sequence of a glutaminase-asparaginase from Acinetobacter glutaminasificans and preliminary crystallographic data for an asparaginase from Erwinia chrysanthemi.

The complete amino acid sequence of a glutaminase-asparaginase from Acinetobacter glutaminasificans, for which a preliminary tertiary structure is available from crystallographic analysis, has been determined by automated Edman degradation of fragments produced by chemical and proteolytic cleavages. The protein consists of 331 amino acid residues and has a molecular weight of 35,500. The pattern of hydrophilic and hydrophobic regions is typical of a globular protein. A new crystal form of an Erwinia chrysanthemi 1125 asparaginase is reported. The space group is monoclinic C2, with unit cell parameters of: a = 107.8, b = 91.7, c = 129.2 A and beta = 91.7 degrees. A Vm of 2.25 A3/dalton was calculated for one tetramer of 35,100-dalton subunits per asymmetric unit. X-ray intensity data have been obtained to 2.2 A resolution. The point group symmetry of the Er. chrysanthemi tetramer is 222 from self-rotation function calculations. The relative orientations of an A. glutaminasificans glutaminase-asparaginase model and the Er. chrysanthemi asparaginase tetramer have been determined with the cross-rotation function, and translation function calculations have revealed a plausible location for the asparaginase tetramer in the crystal.

Acinetobacter↗
PubMed1985

[Purification and properties of N-acyl-amino acid amidohydrolases from Euglena gracilis].

Aminoacylase from Euglena gracilis was purified by gel filtration and DEAE-Sephacel 230 times and analyzed with respect to substrate specificity, effector behaviour, pH optimum, Michaelis constant, electrophoretic mobility and molecular weight. The molecular weight is about 252000 (gel filtration). The properties of the aminoacylase from Euglena gracilis and the acylases I (EC 3.5.1.14) from the human and the pig kidneys were compared. The enzyme could be distinguished immunologically from the renal aminoacylases. No indications for the existence of a separate acylase III or of a deformylase were found.

Amidohydrolases↗