A novel sucrose phosphorylase from the metagenomes of sucrose-rich environment: isolation and characterization

Abstract

Sucrose phosphorylase, an important enzyme mainly involved in the generic starch and sucrose pathways, has now caught the attention of researchers due to its transglycosylation activity. A novel sucrose phosphorylase, unspase, has been isolated, and its transglycosylation properties were characterized. Compared with Bisp, the sucrose phosphorylase from Bifidobacterium adolescentis, unspase had two deleted regions in its C-terminal. These deleted regions were probably equivalent to the important five-stranded anti-parallel β-sheet domain in sucrose phosphorylase. Unspase has a k_m of 21.12 mM, a V_max of 69.24 μmol min⁻¹ mg⁻¹ and a k_cat of 31.19 s⁻¹ with sucrose as substrate. In 3-(N-morpholino) propanesulfonic acid (MOPS) buffer, unspase transferred the glycosyl moiety to l-arabinose, d-fructose and l-sorbose. Much to our surprise, unspase can catalyze the transglycosylation in which a glycosyl moiety was transferred to l-arabinose in the presence of phosphate, which is an interesting exception to the generally accepted fact that transglycosylation can only occur under the condition of phosphate absence. The final yield of the transglycosylation product (37.9 %) in phosphate buffer was even higher than that (5.8 %) in MOPS buffer. This is a novel phenomenon that a sucrose phosphorylase can catalyze a transglycosylation reaction in the presence of phosphate.