Purification and characterization of human microsomal dipeptidase.
Human microsomal dipeptidase (MDP, formerly referred to as dehydropeptidase-I or renal dipeptidase) [EC 3.4.13.11] was solubilized from the membrane fraction of kidney by treatment with octyl-beta-D-glucoside and purified by a procedure including ion exchange chromatography and affinity chromatography on cilastatin-immobilized Sepharose. The purified human MDP was found to be homogeneous on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The apparent molecular weight (Mr) was estimated by SDS-polyacrylamide gel electrophoresis under non-reducing conditions to be 130 kDa, comprising a homodimer of two subunits. After treatment with endoglycosidase F, human MDP showed a single band with an apparent Mr of 42 kDa on SDS-polyacrylamide gel electrophoresis. Human MDP was found to bind to Con A-Sepharose and the activity was eluted with methyl-alpha-D-mannopyranoside, suggesting that human MDP is a glycoprotein. We also examined the substrate specificity of human MDP and found that human MDP catalyzed the hydrolysis of S(substituent)-L-cysteinyl-glycine adducts such as L-cystinyl-bis(glycine) and S-N-ethylmaleimide-L-cysteinyl-glycine, as well as the conversion of leukotriene D4 to leukotriene E4. These results suggest that MDP might play an important role in the metabolism of glutathione and leukotriene.
Suntory Institute for Biomedical Research, Osaka.
H
H
Adachi
I
I
Kubota
N
N
Okamura
H
H
Iwata
M
M
Tsujimoto
H
H
Nakazato
T
T
Nishihara
T
T
Noguchi
D000596:Amino Acids / Q000032:analysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004150:Dipeptidases / Q000032:analysis / Q000276:immunology / Q000302:isolation & purification*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007525:Isoelectric Focusing; D007668:Kidney / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology*; D010455:Peptides / Q000032:analysis
D000596:Amino Acids; D010455:Peptides; D004150:Dipeptidases