The role of dipeptidyl peptidase IV in the cleavage of glucagon family peptides: in vivo metabolism of pituitary adenylate cyclase activating polypeptide-(1-38).
Dipeptidyl peptidase IV (DP-IV) is a cell surface serine dipeptidase that is involved in the regulation of the incretin hormones, glucagon-like peptide (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). There is accumulating evidence that other members of the glucagon family of peptides are also endogenous substrates for this enzyme. To identify candidate substrates for DP-IV, a mass spectrometry-based protease assay was developed that measures cleavage efficiencies (kcat/Km) of polypeptides in a mixture, using only a few picomoles of each substrate and physiological amounts of enzyme in a single kinetic experiment. Oxyntomodulin and the growth hormone-(1-43) fragment were identified as new candidate in vivo substrates. Pituitary adenylate cyclase-activating polypeptide-(1-38) (PACAP38), a critical mediator of lipid and carbohydrate metabolism, was also determined to be efficiently processed by DP-IV in vitro. The catabolism of exogenously administered PACAP38 in wild type and DP-IV-deficient C57Bl/6 mice was monitored by tandem mass spectrometry. Animals lacking DP-IV exhibited a significantly slower clearance of the circulating peptide with virtually complete suppression of the inactive DP-IV metabolite, PACAP-(3-38). These in vivo results suggest that DP-IV plays a major role in the degradation of circulating PACAP38.
Zhu
Lan
L
Metabolic Disorders, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Tamvakopoulos
Constantin
C
Xie
Dan
D
Dragovic
Jasminka
J
Shen
Xiaolan
X
Fenyk-Melody
Judith E
JE
Schmidt
Keith
K
Bagchi
Ansuman
A
Griffin
Patrick R
PR
Thornberry
Nancy A
NA
Sinha Roy
Ranabir
R
D000595:Amino Acid Sequence; D000818:Animals; D002138:Calibration; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D005934:Glucagon / Q000737:chemistry* / Q000378:metabolism*; D006728:Hormones / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D013058:Mass Spectrometry; D051379:Mice; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
C495402:Adcyap1 protein, mouse; D006728:Hormones; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D005934:Glucagon; D018819:Dipeptidyl Peptidase 4