The esterification of N-acetyl-L-tyrosine catalysed by native and immobilized on porous glass highalkaline proteinase from B. alcalophilus PB92 in ethanol was studied. It was observed that native proteinase catalysed synthesis of N-Ac-L-Tyr ethyl ester (ATEE) in environment of 6% water concentration with initial rate 2.5·10^-2 μmol^-1. However immobilized proteinase showed higher activity and stability comparing with her native form. Catalytic activity in cosolvent systems (water concentration 6% ): ethanol-acetone// -acetonitrile// -DMF 1:1 (v/v) was also investigated. Synthesis of ATEE in the presence of acetone and acetonitrile wasn’t observed.