The pectate lyase gene
pelA from alkaliphilic
Bacillus licheniformis strain 14A was cloned and sequenced. The nucleotide sequence corresponded to an open reading frame of 1,026 bp that codes for a 39 amino acid signal peptide and a mature protein with a molecular mass of 33,451 Da. The mature PelA showed significant homology to other pectate lyases belonging to polysaccharide lyase family 1, such as enzymes from different
Bacillus spp. and
Erwinia chrysanthemi. The
pelA gene was expressed in
Escherichia coli as a recombinant fusion protein containing a C-terminal His-tag, allowing purification to near homogeneity in a one-step procedure. The values for the kinetic parameters
K
m and
V
max of the fusion protein were 0.56 g/l and 51 µmol/min, respectively. The activity of purified PelA
His was inhibited in the presence of excess substrate. Characterization of product formation revealed unsaturated trigalacturonate as the main product. The yields of unsaturated trigalacturonic acids were further examined for the substrates polygalacturonic acid, citrus pectin and sugar-beet pectin.