Purification and characterization of soluble invertases from suspension-cultured bamboo (Bambusa edulis) cells

摘要

An alkaline invertase (IT Ⅰ) and an acid invertase (IT Ⅱ) were purified from the soluble fraction of suspension cultured bamboo cells. Both purified invertases were homogeneous as examined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and were identified as β-fructofuranosidases able to attack the β-fructofuranoside from the fructose end. With respect to sucrose hydrolysis, the optimal pHs were 7.0 and 4.5 for IT Ⅰ and IT Ⅱ, respectively. The Km's were 10.9 and 3.7 mM. The IT Ⅰ and IT Ⅱ molecular masses were 240 and 68 kDa, respectively, as estimated by gel filtration. The isoelectric points were 4.8 and 7.4. IT Ⅰ was a homo-tetrameric enzyme activated by bovine serum albumin (BSA). IT Ⅱ was a monomeric enzyme activated by BSA, concanavalin A (ConA) and urease. Both isoforms were significantly inhibited by heavy metal ions Ag~+ (5 mM) and Hg~(2+) (1 mM), and mercaptide forming agent ρ-chloromercuribenzoic acid (PCMB; 0.5 mM).