Lipolytic Enzymes in Myxococcus xanthus
The genome of Myxococcus xanthus encodes lipolytic enzymes in three different families: patatin lipases, α/β hydrolases, and GDSL lipases. One member of each family was characterized. The protein encoded by MXAN_3852 contains motifs characteristic of patatins. MXAN_5522 encodes a protein with the G-X-S-X-G motif characteristic of the lipase subfamily of α/β hydrolases. MXAN_4569 encodes a member of the GDSL family of lipolytic enzymes. Strains with deletions of MXAN_5522 and MXAN_4569 undergo faster development and earlier myxospore formation than the wild-type strain. The MXAN_5522 mutation results in spore yields substantially higher than those seen for wild-type cells. Gene expression analysis using translational lacZ fusions indicates that while all three genes are expressed during development, only MXAN_5522 and MXAN_4569 are expressed during vegetative growth. The proteins encoded by these genes were overexpressed using a T7 RNA polymerase transcription (pET102/D-TOPO) system in Escherichia coli BL21 Star (DE3) cells. The substrate specificities of the purified enzymes were investigated using p-nitrophenyl esters with chain lengths from C2 to C16. These enzymes preferentially hydrolyzed esters of short-chain fatty acids, yielding the highest activity with p-nitrophenyl acetate.