CDNA CLONING AND EXPRESSION OF SECRETED XENOPUS-LAEVIS DIPEPTIDYL AMINOPEPTIDASE-IV

From a Xenopus laevis skin library a cDNA coding for dipeptidyl aminop eptidase IV (DPP IV) was isolated. The ORF codes for a protein with se quence similarity to DPP-IV-like proteins, including mammalian DPP IV and X. laevis fibroblast activation factor. Tn contrast to the membran e-bound mammalian enzymes, mature X. laevis DPP IV is a soluble secret ed polypeptide. The frog enzyme possesses a cleavable signal sequence; the mature protein starts at Thr30 of the polypeptide predicted from the cDNA sequence. Expression of the cloned cDNA by recombinant vaccin ia virus resulted in the formation of a protein with the expected mole cular mass and substrate specificity. Recombinant DPP IV was present i n high concentration in the supernatant of infected cells and exhibite d enzymatic activity towards the synthetic substrate alanyl-prolyl-p-n itroanilide.