Fig. 2

Synonymous codon replacement does not affect the secretion ability of signal peptides. CAI, extracellular & intracellular specific activity of amylase reporter, as well as secretion ability of SP9 (a) and SP13 (b) when codons were de-optimized or optimized. c CAI plots of codon de-optimized and optimized α-mating factor sequences. d Top, western blow showing protein levels of extracellular & intracellular protein levels of amylase reporter in codon de-optimized and optimized strains; middle and bottom, densitometric quantification of western blot results. 6 × His tag antibody and β-Actin antibody were used as primary antibodies to detect AmyA and β-actin (loading control), respectively. The level of aFori-AmyA was set as 1. For enzyme activity and western blot quantification, error bars were calculated as standard deviation of three independent experiments. *, p < 0.05