We have studied the efficiency of N-terminal processing of the antibody light chain depending on the structure of the leader sequence when expressed in the yeast Pichia pastoris. The humanized light kappa-chain of the murine antibody H3-1 and the Saccharomyces cerevisiae alpha-factor pre-pro-leader sequence (pre-pro-alpha-F) were used as models. The use of pre-region of the pre-pro-alpha-F alone or together with the Glu-Ala-linker leads to the slightly increased yield of the secreted L-chain but was accompanied by the incomplete N-terminal processing of the secreted product.