Abstract
Using the classical emulsified system and the monomolecular film technique, the substrate specificity of recombinant Gibberella zeae lipase (rGZEL) that originates from Gibberella zeae was characterized in detail. Under the emulsified reaction system, both phospholipase and glycolipid hydrolytic activities were observed, except for the predominant lipase activity. The optimum conditions for different activity exhibition were also determined. Compared with its lipase activity, a little higher ratio of glycolipid hydrolytic activity (0.06) than phospholipase activity (0.02) was found. rGZEL preferred medium chain-length triglycerides, while lower activity was found for the longer-chain triglyceride. Using the monomolecular film technique, we found that the preference order of rGZEL to different phospholipids was 1,2-diacyl-sn-glycero-3-phospho-l-serine (PS) > 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (PG) > 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) > l-α-phosphatidylinositol (PI) > cardiolipin (CL) > 3-sn-phosphatidic acid sodium salt (PA) > l-α-phosphatidylethanolamine (PE), while no hydrolytic activity was detected for sphingomyelin (SM). Moreover, rGZEL showed higher galactolipase activity on 1,2-distearoyimonoglactosylglyceride (MGDG). A kinetic study on the stereo- and regioselectivity of rGZEL was also performed by using three pairs of pseudodiglyceride enantiomers (DDGs). rGZEL presented higher preference for distal DDG enantiomers than adjacent ester groups, however, no hydrolytic activity to the sn-2 position of diglyceride analogs was found. Furthermore, rGZEL preferred the R configuration of DDG enantiomers. Molecular docking results were in concordance with in vitro tests.