Lipolytic enzymes LipA and LipB from Bacillus subtilis differ in regulation of gene expression, biochemical properties, and three-dimensional structure

Bacillus subtilis secretes the lipolytic enzymes LipA and LipB. We show her e that they are differentially expressed depending on the composition of th e growth medium: LipA is produced in rich and in minimal medium, whereas Li pB is present only in rich medium. A comparison of biochemical characterist ics 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 coord inates from the LipA crystal structure were used to build a three-dimension al structural model of LipB, which revealed that 43 out of 45 residues diff erent from LipA are surface-located allowing to rationalize the differences observed in the substrate preferences of the two enzymes. (C) 2001 Federat ion of European Biochemical Societies. Published by Elsevier Science B.V. A ll rights reserved.