Sugar metabolism and regulation in the hyperthermophilic archaeon Thermococcus litoralis

Abstract

A novel trehalose glycosyl transferring synthase (TreT) from the hyperthermophilic archaeon T. litoralis was identified. This enzyme produces trehalose by the transfer of glucose from ADP-glucose (or, less effectively, UDP-glucose and GDP-glucose) onto the 1-position of glucose to form trehalose and ADP. Such an enzymatic activity in the synthesis of trehalose has not yet been described for any other organisms. It catalyzes a reversible reaction for trehalose synthesis and degradation by converting glucose and ADP-glucose to trehalose and ADP. The enzyme properties were characterized biochemically. The physiological function of TreT in vivo is still not completely understood.An ATP-dependent and fructose-6-phosphate-forming fructokinase (Frk) was also identified and characterized in T. litoralis, which gene locates divergently to the trehalose/maltose transporter. The biochemical properties of this enzyme were characterized in this study.TrmB is a novel archaeal sugar-specific transcriptional repressor regulating the expression of trehalose/maltose ABC transporter dependent on the presence of maltose or trehalose in medium. TrmB binds maltose much stronger than trehalose. TrmB binds to the DNA fragments of the TATA box promoter region and upstream motif of malEFG-operon. TrmB does not bind to MalK.Two enzymes (TreT and FrK) have been identified in this research work and their expressional regulation by TrmB also has been investigated. The further interesting work can focus on the sucrose or trehalose metabolism pathway and the net work of sugar metabolism regulation in T. litoralis.