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PubMed2005

Alteration of leucine aminopeptidase from Streptomyces septatus TH-2 to phenylalanine aminopeptidase by site-directed mutagenesis.

To tailor leucine aminopeptidase from Streptomyces septatus TH-2 (SSAP) to become a convenient biocatalyst, we are interested in Phe221 of SSAP, which is thought to interact with the side chain of the N-terminal residue of the substrate. By using saturation mutagenesis, the feasibility of altering the performance of SSAP was evaluated. The hydrolytic activities of 19 mutants were investigated using aminoacyl p-nitroanilide (pNA) derivatives as substrates. Replacement of Phe221 resulted in changes in the activities of all the mutants. Three of these mutants, F221G, F221A, and F221S, specifically hydrolyzed L-Phe-pNA, and F221I SSAP exhibited hydrolytic activity with L-Leu-pNA exceeding that of the wild type. Although the hydrolytic activities with peptide substrates decreased, the hydrolytic activities with amide and methyl ester substrates were proportional to the changes in the hydrolytic activities with pNA derivatives. Furthermore, based on a comparative kinetic study, the mechanism underlying the alteration in the preference of SSAP from leucine to phenylalanine is discussed.

Aminopeptidases↗
PubMed1985

Purification, preliminary characterization, and immunological comparison of hog lens leucine aminopeptidase (EC 3.4.11.1) with hog kidney and beef lens aminopeptidases.

Leucine aminopeptidase (LAP) was purified from hog lenses by application of the Himmelhoch procedure for isolation of hog kidney LAP [S. R. Himmelhoch (1970) in Methods in Enzymology (Perlmann, G. E., and Lorand, L., eds.), Vol. 19, pp. 508-513, Academic Press, New York.] This involved treating crude hog lens homogenates with hexadecyltrimethylammonium bromide, DEAE-cellulose adsorption and elution, ammonium sulfate fractionation (53-84% of saturation), and gel filtration on a Bio-Gel A-1.5m column. Purifications ranging from 2080- to 4700-fold with activity yields from 28 to 100% were achieved. The hog lens LAP appeared homogeneous by native and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE). Bio-Gel chromatography of the native enzyme and SDS-PAGE of dimethylsuberimidate-crosslinked LAP indicated a molecular weight of 326,000. SDS-PAGE of untreated LAP showed a subunit weight of 54,000, consistent with a hexameric enzyme structure. By immunodiffusion, LAP from hog lens and kidney were identical while hog lens and beef lens enzymes demonstrated only partial identity. Electrophoresis of the native enzymes showed a slightly lower mobility for the hog lens LAP than for beef LAP at pH 8.7.

Animals↗
PubMed1991

Identification of a rat liver dipeptidyl aminopeptidase IV with a liver plasma membrane glycoprotein (gp110). A study using dipeptidyl aminopeptidase IV-deficient rats.

A rat liver plasma membrane glycoprotein, gp110, was compared with dipeptidyl aminopeptidase IV (DAP IV) by using Wistar rats (DAP IV-positive rats) and Fischer 344 rats (DAP IV-negative rats). Fischer rats also lacked gp110 and gp110 of Wistar rats had DAP IV activity. Furthermore, we showed that the C-terminal sequence of gp110 was Ser-Leu-Arg, which was the same as the C-terminal amino acid sequence deduced from the nucleotide sequence of the cDNA of DAP IV. According to these results, we concluded that gp110 was identical with DAP IV.

Amino Acid Sequence↗
PubMed2001

Synergistic action of an X-prolyl dipeptidyl aminopeptidase and a non-specific aminopeptidase in protein hydrolysis.

Non-specific monoaminopeptidase (AP; E.C. 3.4.11) and X-prolyl dipeptidyl aminopeptidase (X-PDAP; E.C. 3.4.14.5), both from Aspergillus oryzae, demonstrate strong synergism in hydrolyzing proline-containing peptides. Incubation of AP alone with the peptide Ala-Pro-Gly-Asp-Arg-Ile-Tyr-Val-His-Pro-Phe does not generate free amino acids. However, when AP and X-PDAP are added in combination, complete and immediate hydrolysis of all peptide bonds, other than X-Pro bonds, is observed. In the enzymatic hydrolysis of casein, soy, and gluten, degree of hydrolysis (DH) values of 54, 54, and 47% were achieved, respectively, when subtilisin (E.C. 3.4.21.62) was supplemented with AP. Addition of a third enzyme, X-PDAP, resulted in significantly higher DH values of 69, 72, and 64%, respectively, establishing the utility of this synergism in protein hydrolysis.

Amino Acids↗
PubMed1982

Purification of dipeptidyl-aminopeptidase IV from human kidney by anti dipeptidyl-aminopeptidase IV affinity chromatography.

Dipeptidyl-aminopeptidase IV (DAP-IV) was purified 850 fold with a yield of 16.5% from human kidney cortex. Only two chromatographic procedures of DEAE-cellulose and anti DAP-IV Sepharose were used. The purified enzyme was shown to be homogeneous by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate. Among various substrates with the structure of X-Y-p-nitroanilide, Lys-Pro-Gly-Pro- and Arg-Pro-p-nitroanilides were hydrolyzed very fast by DAP-IV. Optimum pH of DAP-IV in human kidney was pH 8.7, Km value for Gly-Pro-pNA was 2.51 +/- 0.01 x 10(-4) M and V max was 66.6 +/- 0.7 mumol/min/mg protein. Diisopropylfluorophosphate completely inhibited DAP-IV at 0.1 mM. However, the enzyme was almost unaffected by N-ethylmaleimide, p-chloromercuribenzoate, iodoacetate, phenylmethylsulfonylfluoride, and several metals. The amino acid composition of DAP-IV purified from human kidney was similar to that of DAP-IV purified from pig kidney, liver and intestine. These results indicate that the properties of DAP-IV purified from human kidney are almost same as those from pig kidney.

Antibodies↗
PubMed1987

Serum activities of dipeptidyl-aminopeptidase II and dipeptidyl-aminopeptidase IV in tumor-bearing animals and in cancer patients.

Serum activities of dipeptidyl-aminopeptidases (DAP) II and IV were measured in tumor-bearing animals and in patients with blood and solid cancers using highly sensitive and specific fluorometric methods. In mice with intraperitoneal or subcutaneous implantation of Ehrlich ascites tumor cells, serum DAP II activity was increased and serum DAP IV activity was decreased, resulting in a significant increase in the ratio of serum DAP II and DAP IV activities. The increase in the ratio of these two activities paralleled the size of the subcutaneous tumors. However, both serum DAP II and DAP IV activities were increased in rats with experimental hepatic cancer induced by 3'-methyl-4-dimethylaminoazobenzene, and the increase in the ratio of the two activities was not significant. In cancer patients, as compared with healthy subjects, serum DAP II activity was increased and serum DAP IV activity was decreased, the ratio of serum DAP II and DAP IV activities being markedly increased in cancer patients. Both serum DAP II and DAP IV activities were increased in patients with hepatic cancer as were those in rats with hepatic cancer, but the increase in DAP II was greater than that of DAP IV; thus the ratio of the two activities increased significantly. These data suggest that the increase of the serum DAP II/DAP IV ratio could be a biochemical index of cancer.

Adult↗