The glucose effect and regulation of α-amylase synthesis in the hyperthermophilic archaeon Sulfolobus solfataricus

An α-amylase was purified from culture supernatants of Sulfolobus solfataricus 98/2 during growth on starch as the sole carbon and energy source. The enzyme is a homodimer with a subunit mass of 120 kDa. It catalyzes the hydrolysis of starch, dextrin, and α-cyclodextrin with similar efficiencies. Addition of exogenous glucose represses production of α- amylase, demonstrating that a classical glucose effect is operative in this organism. Synthesis of [³⁵S]-α-amylase protein is also subject to the glucose effect. α-Amylase is constitutively produced at low levels but can be induced further by starch addition. The absolute levels of α-amylase detected in culture supernatants varied greatly with the type of sole carbon source used to support growth. Aspartate was identified as the most repressing sole carbon source for α-amylase production, while glutamate was the most derepressing. The pattern of regulation of α-amylase production seen in this organism indicates that a catabolite repression-like system is present in a member of the archaea.