An unusual pectate lyase from a Bacillus sp with high activity on pectin: cloning and characterization

The gene pelA encoding a pectate lyase from the strain Bacillus sp, BP-23 w as cloned and expressed in Escherichia coli, The nucleotide sequence of a 1 214 bp DNA fragment containing pelA gene was determined, revealing an ORF o f 666 nucleotides that encoded a protein of 23 233 Da. The deduced amino ac id sequence of the encoded enzyme showed homology to pectate lyases A, B, C and D from Fusarium solani, Pel-3 and PelB from Erwinia carotovora and Pel l from Erwinia chrysanthemi, Homology was also found to the protein deduced from the Bacillus subtilis yvpA gene, the function of which is unknown. Th e heterologous expressed enzyme depolymerized polygalacturonate and pectins of methyl esterification degree from 22 to 89 %, and exhibited similar act ivity on polygalacturonate and on 89% esterified citrus pectin. Optimum tem perature and ph for enzymic activity were 50 degrees C and pH 10, respectiv ely. Ca2+ was required for activity on pectic substrates, while the enzyme was strongly inhibited by Ba2+.