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.
Iwaki-Egawa
S
S
Department of Clinical Biochemistry, Hokkaido College of Pharmacy, Otaru, Hokkaido, 047-0264, Japan. sachiko@hokuyakudai.ac.jp
Watanabe
Y
Y
Kikuya
Y
Y
Fujimoto
Y
Y
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