Uses
Human dipeptidyl peptidase IV has been used in a study to assess the interactive hemodynamic effects of its inhibition as well as the angiotensin-converting enzyme inhibition. Human dipeptidyl peptidase IV has also been used in a study to identify and characterize the 100 kDa High Molecular Weight Hymenoptera Venom Allergens Api m 5 and Ves v 3.
General Description
Dipeptidyl Peptidase IV (DPP4) is mapped to human chromosome 2q24.2. It comprises the N-glycosylation sites located in the β-propeller domain.
Biochem/physiol Actions
Native DPPIV is a ubiquitous type II transmembrane glycoprotein and a serine protease of the S9 prolyl-oligopeptidase family. In vivo, it is synthesized with a signal peptide, which functions as the membrane anchoring domain. There is an 88% sequence homology between the human and porcine kidney enzymes. Both exist as homodimers with a subunit molecular weight of ~30 kDa. The high mannose 100 kDa DPPIV precursor is processed in the Golgi to yield a 124 kDa heavily N-and O-linked mature glycoprotein. It is then sorted to the apical membrane through the concerted action of both N- and O-linked glycans and its association with lipid microdomains. The porcine enzyme contains 18.3% carbohydrates, which the glycan composition is 0.9% fucose, 3.4% mannose, 5.1% galactose, 8.2% glucosamine, and 0.7% sialic acid. DPPIV is highly expressed on endothelial cells, epithelial cells, and lymphocytes. It is also present in plasma in its soluble form.
Purification Methods
The aminopeptidase is purified about 2000-fold by column chromatography on CM-cellulose, hydroxylapatite and Gly-Pro AH-Sepharose. [Imai et al. J Biochem (Tokyo) 93 431 1983, Schomburg & Schomburg Springer Handbook of Enzymes 2nd Edn vol 6 p 286 2002.] DNA (deoxyribonucleic acids). The essential structures of chromosomes are DNA and contain the genetic “blueprint” in the form of separate genes. They are made up of the four deoxyribonucleic acids (nucleotides): adenylic acid, guanylic acid, cytidylic acid and thymidylic acid (designated A, G, C, T respectively) linked together by their phosphate groups in ester bonds between the 3' and 5' hydroxy groups of the 2'-deoxy-D-ribose moiety of the nucleotides. The chains form a double-stranded spiral (helix) in which the two identical nucleotide sequences run antiparallel with the heterocyclic bases hydrogen bonded (A….T, G….C) forming the “ladder” between the strands. Short sequences of DNA are available commercially, are commercially custom made or synthesised in a DNA synthesiser and purified by HPLC. Their purity can be checked by restriction enzyme cleavage followed by gel electophoresis, or directly by gel electrophoresis or analytical HPLC. Commercial DNAs are usually pure enough for direct use but can be further purified using commercially available kits involving binding to silica or other matrices and eluting with Tris buffers. There are now rapid “throughput” techniques for sequencing DNA which are very accurate.
