Cloning, nucleotide sequencing, and expression of the .BETA.-galactosidase-encoding gene (lacA) from Aspergillus oryzae.

Abstract

IntroductionAspergillus oryzae is a filamentous fungus which has been used for centuries in fermentation of several traditional Japanese and Asian foodstuffs such as sake (rice wine), shoyu (soy sauce), and miso (soybean paste). A. oryzae is known to produce and secrete several glycosidases including a-amylase, glucoamylase, and a-glucosidase, which play an important role in those fermentations. A. oryzae also excretes b-galactosidase (b-gal; EC 3.2.1.23.) (Akasaka et al., 1976;Tanaka et al., 1975), which hydrolyzes bgalactoside bond and is alternatively called lactase since lactose in milk is one of the natural substrates of the enzyme. The A. oryzae b-gal is commercially available from several suppliers and is used in the treatment of milk and whey in order to make dairy products sweeter and more affordable to those who suffer lactose-intolerance. The enzyme has also been used in the synthesis of galactose-containing oligosaccharides via transgalactosylation (Binder et al., 1994;Reuter et al., 1999;Toba et al., 1985) or reversed hydrolysis (Ajisaka et al., 1988).In spite of its usefulness, there have been a few studies focused on fungal b-gal genes. Cloning and expression in Saccharomyces cerevisiae was reported for cDNA of the b-gal gene (lacA) from Aspergillus niger (Kumar et al., 1992

Investigating thermal stability based on the structural changes of lactase enzyme by several orthogonal methods

“…According to the information in the UNIprot database [ 6 ], the weight of β-galactosidase from Aspergillus oryzae is 109 kDa. This information is based on the amino acid sequence and does not take into account possible structural modifications.…”

“…usually contain one specific stream of lactase derived from Aspergillus oryzae (Yellow koji mold), also called Tilactase [ 5 ]. The beta-galactosidase produced by this medically and industrially important filamentous fungus is a relatively big and complex glycoprotein, which contains 1009 amino acids, and has an estimated molecular mass of 109 kDa without the post translational modifications [ 6 ].…”

Cooperation between β‐galactosidase and an isoprimeverose‐producing oligoxyloglucan hydrolase is key for xyloglucan degradation in Aspergillus oryzae

“…This gene was cloned and termed lacA by Ito et al . and the crystal structure of the corresponding enzyme (LacA) was previously resolved by Maksimainen et al . .…”

“…In the current study, we determined that a gene encoding A. oryzae b-galactosidase was induced in the presence of xyloglucan oligosaccharides. This gene was cloned and termed lacA by Ito et al [20] and the crystal structure of the corresponding enzyme (LacA) was previously resolved by Maksimainen et al [21]. Based on the amino acid sequence analyses of LacA, this enzyme is likely involved in lactose hydrolysis.…”