Dipeptidyl peptidase IV from human serum: purification, characterization, and N-terminal amino acid sequence.
Dipeptidyl peptidase IV (DPP IV) in normal human serum was purified 14,400-fold with a 25% yield to homogeneity. The molecular weight of the purified enzyme was approximately 110,000 on SDS-PAGE, almost the same as that of human kidney membrane-bound DPP IV. No difference was found between the two enzymes enzymologically and immunologically, either in substrate specificity, susceptibility to inhibitors, or cross-reactivity with an anti-rat kidney DPP IV antibody, or in their ability to bind adenosine deaminase. However, the N-terminal amino acid sequence of serum DPP IV lacked the transmembrane domain of the membrane-bound enzyme and started at the 39th position, serine, from the N-terminus predicted from the cDNA nucleotide sequence. These results suggest that membrane-bound DPP IV loses its transmembrane domain upon release into the serum, and that its structure on the plasma membrane is not required for its binding to adenosine deaminase.
Department of Clinical Biochemistry, Hokkaido College of Pharmacy, Otaru, Hokkaido, 047-0264, Japan. sachiko@hokuyakudai.ac.jp
S
S
Iwaki-Egawa
Y
Y
Watanabe
Y
Y
Kikuya
Y
Y
Fujimoto
D000243:Adenosine Deaminase / Q000378:metabolism; D000581:Amidohydrolases / Q000378:metabolism; D000595:Amino Acid Sequence; D018819:Dipeptidyl Peptidase 4 / Q000097:blood* / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D007668:Kidney / Q000201:enzymology; D008969:Molecular Sequence Data; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid
D018819:Dipeptidyl Peptidase 4; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D000243:Adenosine Deaminase