Endo-β-Glucanase Secreted by a Psychrotrophic Yeast: Purification and Characterization

Abstract

A psychrotrophic yeast, Rhodotorula glutinis KUJ 2731, isolated from soil, effectively produced an extracellular endo-β-glucanase (EC 3.2.1.4). The enzyme was monomeric, and the molecular mass was about 40,000 Da. The N-terminal amino acid sequence was H-Ser-Leu-Pro-Lys-Leu-Gly-Gly-Val-Asp-Leu-Ala-Gly-Leu-Asp-Ile-Gly- Lys-Asp-Lys-Asn-. α-Helix content was calculated to be about 32.6%. The isoelectric point was 8.57. The activation energy was 20.9 kJ/mol, which was much smaller than that of mesophilic enzymes. The enzyme was active at temperatures from 0 to 70°C, with a highest initial velocity at 50°C similar to other psychrotrophic enzymes. The enzyme was inhibited by Hg²⁺. The enzyme catalyzed hydrolysis of carboxymethyl cellulose with an apparent K_m of 1.1% and V_max of 556 μmol/min/mg. Products from the enzymatic hydrolysis of carboxymethyl cellulose by the enzyme were glucose, cellobiose, and cellotriose. The enzyme also catalyzed the transglycosylation of p-nitrophenyl-β-cellotrioside to cellotetraose.

• psychrotrophic yeast
• endo-β-glucanase
• Rhodotorula glutinis
• transglycosylation