title: Dipeptidyl peptidase IV activity in commercial solutions of human serum albumin.
abstract: Due to the heterogeneous nature of commercial human serum albumin (cHSA), other components, such as the protease dipeptidyl peptidase IV (DPP-IV), possibly contribute to the therapeutic effect of cHSA. Here, we provide evidence for the first time that DPP-IV activity contributes to the formation of aspartate-alanine diketopiperazine (DA-DKP), a known immunomodulatory molecule from the N terminus of human albumin. cHSA was assayed for DPP-IV activity using a specific DPP-IV substrate and inhibitor. DPP-IV activity was assayed at 37 and 60°C because cHSA solutions are pasteurized at 60°C. DPP-IV activity in cHSA was compared with other sources of albumin such as a recombinant albumin (rHSA). In addition, the production of DA-DKP was measured by negative electrospray ionization/liquid chromatography mass spectrometry (ESI(-)/LCMS). Significant levels of DPP-IV activity were present in cHSA. This activity was abolished using a specific DPP-IV inhibitor. Fully 70 to 80% DPP-IV activity remained at 60°C compared with the 37°C incubate. No DPP-IV activity was present in rHSA, suggesting that DPP-IV activity is present only in HSA produced using the Cohn fractionation process. The formation of DA-DKP at 60°C was observed with the DPP-IV inhibitor significantly decreasing this formation. DPP-IV activity in cHSA results in the production of DA-DKP, which could account for some of the clinical effects of cHSA.
authors.affiliation: Trauma Research Laboratory, Swedish Medical Center, Englewood, CO 80113, USA. dbaror@ampiopharma.com
authors.forename: David
authors.initials: D
authors.lastname: Bar-Or
authors.forename: Denetta S
authors.initials: DS
authors.lastname: Slone
authors.forename: Charles W
authors.initials: CW
authors.lastname: Mains
authors.forename: Leonard T
authors.initials: LT
authors.lastname: Rael
mesh_terms: D000409:Alanine / Q000096:biosynthesis; D001224:Aspartic Acid / Q000096:biosynthesis; D054659:Diketopiperazines / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry / Q000378:metabolism*; D004340:Drug Contamination; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D012709:Serum Albumin; D012996:Solutions
chemical_list: D054659:Diketopiperazines; D012709:Serum Albumin; D012996:Solutions; D001224:Aspartic Acid; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4; D000409:Alanine
keywords: Cohn fractionation; Diketopiperazine; Dipeptidyl peptidase IV; Human serum albumin; Inflammation