Isolation and analysis of genes for amylolytic enzymes of the hyperthermophilic bacterium Thermotoga maritima

Abstract

In addition to the previously identified 4-α-glucanotransferase gene mgtA and the α-amylase gene amyA of Thermotoga maritima strain MSB8 we have now isolated three further genes encoding amylolytic enzymes from a gene library of this ancestral bacterium. The genes code for the extremely thermostable enzymes pullulanase ( pulA), maltodextrin phosphorylase ( agpA) and α-glucosidase ( aglA) and have the potential to encode polypeptides with calculated molecular masses of 96.3 kDa, 96.1 kDa and 52.5 kDa, respectively. Comparative amino acid sequence analysis revealed that PulA and AgpA are clearly related to other known enzymes with similar function. AglA, on the other hand, was not related to other α-glucosidases but appears to belong to an enzyme family containing α-galactosidases and 6-phospho-β-glucosidases. Enzyme properties are reported which demonstrate the extreme thermostability of these T. maritima enzymes.