Lipolytic enzymes LipA and LipB from <i>Bacillus subtilis</i> differ in regulation of gene expression, biochemical properties, and three‐dimensional structure

Abstract

Bacillus subtilis secretes the lipolytic enzymes LipA and LipB. We show here that they are differentially expressed depending on the composition of the growth medium: LipA is produced in rich and in minimal medium, whereas LipB is present only in rich medium. A comparison of biochemical characteristics revealed that LipB is thermostable at pH 11 but becomes thermolabile at pH 5. However, construction of a variant carrying the substitution A76G in the conserved lipase pentapeptide reversed these effects. The atomic coordinates from the LipA crystal structure were used to build a three-dimensional structural model of LipB, which revealed that 43 out of 45 residues different from LipA are surface-located allowing to rationalize the differences observed in the substrate preferences of the two enzymes.