Functional expression in Pichia pastoris of an acidic pectin methylesterase from jelly fig (Ficus awkeotsang)

Abstract

A cDNA fragment encoding an acidic pectin methylesterase (PME) of jelly fig achene was successfully expressed in Pichia pastoris under the control of the glyceraldehydes-3-phosphate dehydrogenase promoter. The recombinant PME was produced as a secretory protein by N-terminal fusion of a cleavable prepropeptide for signal trafficking, and thus easily harvested from the culture medium. Compared with native N-glycosylated PME (38 kDa) purified from jelly fig achenes, this recombinant PME (45 kDa) appeared to be hyperglycosylated. Activity staining indicated that the recombinant PME was functionally active. Yet the hyperglycosylated recombinant PME possessed thermostability and enzymatic capability over a broad pH range equivalent to those of the native PME, The success of functional production of this acidic jelly fig PME in P. pastoris has significantly broadened its applications in industry.