Characterization of γ-Glutamyl Hydrolase Produced byBacillussp. Isolated from Thai Thua-nao

Abstract

-Glutamyl hydrolase with a molecular mass of 28 kDa was purified from the culture broth of Bacillus sp. isolated from Thai Thua-nao, a natto-like fermented soybean food. The purified enzyme hydrolyzed chemically synthesized oligo--L-glutamates but not oligo--D-glutamates and degraded -polyglutamic acid to a hydrolyzed product of only about 20 kDa (with D-and L-glutamic acid in a ratio of 70:30), suggesting that the enzyme is a -glutamyl hydrolase that cleaves theglutamyl linkage between L-and L-glutamic acid ofpolyglutamic acid.

Volatile profiles of thua nao, a Thai fermented soy product

“…isolated from Thai traditional thua nao could produce several extracellular enzymes with the same function, such as nattokinase, protease, amylase, phytase, lipases and glutamyl hydrolase (Chantawannakul, Oncharoan, Klanbut, Chukeatirote, & Lumyong, 2002;Chukeatirote et al, 2006;Chunhachart, Itoh, Sukchotiratana, Tanimoto, & Tahara, 2006;Dajanta et al, 2009;Visessanguan, Benjakul, Potachareon, Panya, & Riebroy, 2005). Enzymatic degradation products, such as dicarbonyl compounds and free amino acids, will generate further complex odourous compounds through Strecker degradation and other reactions in Maillard browning.…”

Knockout of pgdS and ggt genes improves γ‐PGA yield in B. subtilis

“…Degradation of γ‐PGA is assumed to occur in two sequential steps: initially, an endo‐type hydrolase fragments the polymer, thus increasing its concentration; after that, the exo‐type hydrolase activity of γ‐glutamyl transferase, GGT, can efficiently degrade it, releasing glutamic acid monomers from the smaller and more abundant γ‐PGA fragments (Kimura and Fujimoto, 2010; Kimura et al, 2004; Yao et al, 2009). In B. subtilis the initial polymer fragmentation has been ascribed to PgdS (Ashiuchi et al, 2003, 2006; Chunhachart et al, 2006b; Suzuki and Tahara, 2003; Yao et al, 2009), encoded by the pgdS gene (formerly ywtD ), which is located just downstream of the biosynthetic pgsBCAAE operon. PgdS is a 413 amino acid protein with a signal peptide that directs it to the extra‐cellular space (Hirose et al, 2000), and belongs to the DL‐endopeptidase II family, as B. subtilis LytF and LytC, involved in cell separation (Vollmer et al, 2008).…”

Enhanced expression ofpgdSgene for high production of poly-γ-glutamic aicd with lower molecular weight inBacillus licheniformisWX-02

“…In B. subtilis , the pgds gene has been cloned and expressed in Escherichia coli , and the enzyme properties of PgdS were characterized . The PgdS, identified as an endo‐type hydrolase, can fragment the polymer to reduce the molecular weight . The exo‐type hydrolase GGT, a well‐studied enzyme, can degrade γ‐PGA to release glutamic acid monomers to reduce the concentration …”