Factors mediating activity, selectivity, and substrate specificity for the thiamin diphosphate-dependent enzymes benzaldehyde lyase and benzoylformate decarboxylase.
Benzaldehyde lyase from Pseudomonas fluorescens and benzoylformate decarboxylase from Pseudomonas putida are homologous thiamin diphosphate-dependent enzymes that catalyze carboligase and carbolyase reactions. Both enzymes catalyze the formation of chiral 2-hydroxy ketones from aldehydes. However, the reverse reaction has only been observed with benzaldehyde lyase. Whereas benzaldehyde lyase is strictly R specific, the stereoselectivity of benzoylformate decarboxylase from P. putida is dependent on the structure and orientation of the substrate aldehydes. In this study, the binding sites of both enzymes were investigated by using molecular modelling studies to explain the experimentally observed differences in the activity, stereo- and enantioselectivity and substrate specificity of both enzymes. We designed a detailed illustration that describes the shape of the binding site of both enzymes and sufficiently explains the experimental effects observed with the wild-type enzymes and different variants. These findings demonstrate that steric reasons are predominantly responsible for the differences observed in the (R)-benzoin cleavage and in the formation of chiral 2-hydroxy ketones.
Knoll
Michael
M
Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany.
Müller
Michael
M
Pleiss
Jürgen
J
Pohl
Martina
M
D000446:Aldehyde-Lyases / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000737:chemistry*
D020536:Enzyme Activators; D002262:Carboxy-Lyases; C019778:benzoylformate decarboxylase; D000446:Aldehyde-Lyases; C059416:benzaldehyde lyase; D013835:Thiamine Pyrophosphate