Some Properties of Phosphate-Repressible and -Constitutive Acid Phosphatases of Baker's Yeast

Abstract

Inorganic phosphate-repressible and -constitutive acid phosphatases of baker's yeast were examined to determine whether these two acid phosphatases are the same or different mole-cular species. In DEAE-cellulose chromatography, the repressible enzyme was eluted by 50mM malonate buffer (pH 5.5), whereas the constitutive one was eluted by a much higher buffer concentration. Both enzymes showed non-specific acid phosphatase activities but no phosphodiesterase activity. The repressible enzyme was more sensitive to heat treatment and to chemicals such as Zn²⁺, Hg²⁺, ICH₂CONH₂, PCMB, NaF, urea and Triton X-100 than the constitutive one. Optimum pH of the repressible enzyme was 4.3 whereas that of the consti-tutive one was 3.6, and Km of the repressible enzyme for p-nitrophenylphosphate was 0.74×10^-3 as and that of the constitutive one was 1.1×10^-3M; both of them were competitively inhibited by inorganic phosphate. These results suggest that both enzymes represent different molecular species.