Dipeptidyl aminopeptidase processing and biosynthesis of alkaline extracellular protease from Yarrowia lipolytica.

Alkaline extracellular protease (AEP) from Yarrowia lipolytica is synthesized as a precursor with a 157 aa prepro-region. Signal peptide cleavage was shown to occur after Ala15 by N-terminal amino acid radiosequencing of the largest intracellular AEP precursor. AEP proteolytic activity was not required for AEP processing. After a change of the putative active site Ser to Ala, inactive AEP with the same mobility on SDS-PAGE as wild-type mature AEP was secreted. The role of dipeptidyl aminopeptidase (DPAPase) activity in AEP processing was also investigated. Mutations early in the -X-Ala- and -X-Pro- dipeptide stretch (Pro17 to Met which should prevent DPAPase processing and Ala19 to Val which should allow removal of only the first dipeptide) did not prevent synthesis of active mature AEP nor did use of the DPAPase inhibitor ProboroPro. Deletion of the entire dipeptide stretch (Ala16 to Pro33) resulted in intracellular accumulation of an AEP precursor, which surprisingly was not glycosylated, and little or no secretion of AEP-related polypeptides. Expression of AEP in wild-type and dpp1 dap2 Saccharomyces cerevisiae strains (lacking both the Golgi and vacuolar DPAPases) resulted in secretion of only mature AEP and no AEP precursors. Transit times and levels of AEP secretion were similar for both strains. These results indicate that the KEX2-like cleavage after Lys156-Arg157, which yields mature active AEP can occur in the absence of DPAPase processing and that DPAPase processing is not necessary for secretion of mature active AEP.