The His gap motif in microbial lipases: a determinant of stereoselectivity toward triacylglycerols and analogs.
Lipases preferably hydrolyze the sn-1 and sn-3 acyl chain of triacylglycerols and sn-2 substituted analogs. Molecular modeling studies of the stereopreference of microbial lipases from Rhizopus oryzae, Rhizomucor miehei, Candida rugosa, and lipase B from Candida antarctica toward the hydrolysis of triacylglycerols and analogs revealed that sterical interactions occurring between the sn-2 substituent and the His gap affect substrate geometry, which can be monitored by a single torsion angle. This torsion angle correlates to the experimentally determined stereopreference and is, therefore, suitable to predict stereopreference by molecular modeling. For a given microbial lipase, stereopreference can be estimated by measuring the distance between the side chains of the His gap residues: a narrow His gap cleft implies sn-3 stereopreference for all investigated substrates; a medium-sized His gap discriminates by flexibility of the substrates: flexible substrates are hydrolyzed in sn-1, while rigid substrates are hydrolyzed in sn-3. A wide open His gap implies sn-1 stereopreference for all substrates. This rule holds for all investigated microbial wild type lipases and mutants.
Pleiss
J
J
Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany.
Scheib
H
H
Schmid
R D
RD
D020816:Amino Acid Motifs; D005658:Fungi / Q000201:enzymology*; D006639:Histidine / Q000737:chemistry*; D008049:Lipase / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D014280:Triglycerides / Q000378:metabolism*
D014280:Triglycerides; D006639:Histidine; D008049:Lipase