Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DPP8 is a new member of the prolyl dipeptidases, many of which have important biological functions in vivo. DPP8 catalyzes the cleavage at the carboxyl side of the proline residue at the penultimate position. To study its structure and biochemical properties, we have overexpressed the human DPP8 protein in baculovirus infected Sf9 cells. The protein is soluble and can be purified to homogeneity. Using the chromogenic H-Gly-Pro-pNA as the substrate, a kinetic study shows that purified DPP8 is active and has a similar kcat value as that of DPP-IV, a prolyl dipeptidase that is a drug target for type II diabetes. The kinetic constants of DPP8 are also determined for other chromogenic substrates, and the results indicate that DPP8 has substrate preference at both the P1 and P2 sites. The expression system provides means of better understanding the structure, catalytic mechanism, and biological function of DPP8 protein.
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PMID:Purification and characterization of human prolyl dipeptidase DPP8 in Sf9 insect cells. 1503 77

DPP-IV is a prolyl dipeptidase, cleaving the peptide bond after the penultimate proline residue. It is an important drug target for the treatment of type II diabetes. DPP-IV is active as a dimer, and monomeric DPP-IV has been speculated to be inactive. In this study, we have identified the C-terminal loop of DPP-IV, highly conserved among prolyl dipeptidases, as essential for dimer formation and optimal catalysis. The conserved residue His750 on the loop contributes significantly for dimer stability. We have determined the quaternary structures of the wild type, H750A, and H750E mutant enzymes by several independent methods including chemical cross-linking, gel electrophoresis, size exclusion chromatography, and analytical ultracentrifugation. Wild-type DPP-IV exists as dimers both in the intact cell and in vitro after purification from human semen or insect cells. The H750A mutation results in a mixture of DPP-IV dimer and monomer. H750A dimer has the same kinetic constants as those of the wild type, whereas the H750A monomer has a 60-fold decrease in kcat. Replacement of His750 with a negatively charged Glu (H750E) results in nearly exclusive monomers with a 300-fold decrease in catalytic activity. Interestingly, there is no dynamic equilibrium between the dimer and the monomer for all forms of DPP-IVs studied here. This is the first study of the function of the C-terminal loop as well as monomeric mutant DPP-IVs with respect to their enzymatic activities. The study has important implications for the discovery of drugs targeted to the dimer interface.
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PMID:One site mutation disrupts dimer formation in human DPP-IV proteins. 1544 55

DPP8 is a prolyl dipeptidase homologous to DPP-IV, which is a drug target for Type II diabetes. The biological function of DPP8 is not known. To identify potent and selective chemical compounds against DPP8, we have synthesized a series of isoquinoline and isoindoline derivatives and have tested their inhibitory activity against DPP8, DPP-IV and DPP-II. Isoindoline derivatives were found to be more potent DPP8 inhibitors than isoquinoline derivatives. Isoindoline with a 1-(4,4'-difluor-benzhydryl)-piperazine group at the P2 site was observed to be a very potent DPP8 inhibitor, having an IC(50) value of 14nM with at least a 2500-fold selectivity over either DPP-IV or DPP-II. From SAR results, we speculate that the S1 site of DPP8 may be larger than that of DPP-IV, which would allow the accommodation of larger C-terminal residues, such as isoquinoline or isoindoline.
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PMID:Novel isoindoline compounds for potent and selective inhibition of prolyl dipeptidase DPP8. 1566 38

The prolyl dipeptidase DPP-IV plays diverse and important roles in cellular functions. It is a membrane-bound exoprotease involved in the proteolytic cleavage of several insulin-sensing hormones. The inhibition of its enzymatic activity has been proven effective in the treatment of type II diabetes. Homodimeric DPP-IV interacts extracellularly with adenosine deaminase, and this interaction is critical for adenosine signaling and T-cell proliferation. In this study, we investigated the contribution of hydrophobic interactions to the dimerization of DPP-IV. Hydrophobic residues F713, W734, and Y735 were found to be essential for DPP-IV dimerization. Moreover, the enzymatic activity of DPP-IV was correlated with its quaternary structure. Monomeric DPP-IV had only residual activity left, ranging from 1/30 to 1/1600 of the dimeric forms. Using a surface plasmon resonance technique, we demonstrated that the affinity of these DPP-IV monomers for adenosine deaminase was not significantly altered, compared to that of dimeric DPP-IV. The study not only identifies the hydrophobic interactions critical for DPP-IV dimer formation, but also reveals no global conformational change upon the formation of monomers as determined by the protein-protein interaction (Kd) of DPP-IV with adenosine deaminase.
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PMID:Identification of hydrophobic residues critical for DPP-IV dimerization. 1675 91