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Lipolytic enzymes LipA and LipB from Bacillus subtilis differ in regulation of gene expression, biochemical properties, and three-dimensional structure
Authors:Eggert T  van Pouderoyen G  Dijkstra B W  Jaeger K E
Institution:Lehrstuhl Biologie der Mikroorganismen, Ruhr-Universit?t Bochum, Germany.
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.
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