Cloning and sequencing of a high-alkaline pectate lyase gene from an alkaliphilic Bacillus isolate

Alkaliphilic Bacillus sp. strain KSM-P103 was found to exoproduce a high-alkaline pectate lyase (pectate transeliminase, EC 4.2.2.2). The gene for this enzyme from the alkaliphile was cloned and sequenced for the first time. The structural gene contained a 1,038-bp open reading frame encoding 345 amino acids. The deduced amino acid sequence of the mature enzyme (302 amino acids, 33,312 Da), designated Pel-103, showed very low similarity to those of known pectate lyases with 28-36% identity: the loop regions were very short and the amino acid usage in the parallel beta-helix core structure was considerably different. Moreover, physicochemical and catalytic properties of Pel-103 were different from those of other enzymes reported so far. Pel-103 was a very basic protein with an isoelectric point close to pH 10.5 and had optimal activity at 60-65 degrees C and at pH as high as 10.5. However, Pel-103 appeared to have a similar core and active site topology to the enzymes of known structure from Erwinia chrysanthemi and Bacillus subtilis. Expression of the gene for Pel-103 in B. subtilis resulted in high pectate lyase activity in the culture broth, concomitant with the appearance of a main protein band on an SDS gel at 33 kDa.