Structure of a novel enzyme that catalyzes acyl transfer to alcohols in aqueous conditions.
The unusual architecture of the enzyme (MsAcT) isolated from Mycobacterium smegmatis forms the mechanistic basis for favoring alcoholysis over hydrolysis in water. Unlike hydrolases that perform alcoholysis only under anhydrous conditions, MsAcT demonstrates alcoholysis in substantially aqueous media and, in the presence of hydrogen peroxide, has a perhydrolysis:hydrolysis ratio 50-fold greater than that of the best lipase tested. The crystal structures of the apoenzyme and an inhibitor-bound form have been determined to 1.5 A resolution. MsAcT is an octamer in the asymmetric unit and forms a tightly associated aggregate in solution. Relative to other structurally similar monomers, MsAcT contains several insertions that contribute to the oligomerization and greatly restrict the shape of the active site, thereby limiting its accessibility. These properties create an environment by which MsAcT can catalyze transesterification reactions in an aqueous medium and suggests how a serine hydrolase can be engineered to be an efficient acyltransferase.
Mathews
Irimpan
I
Stanford Synchrotron Research Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
Soltis
Michael
M
Saldajeno
Mae
M
Ganshaw
Grant
G
Sala
Rafael
R
Weyler
Walter
W
Cervin
Marguerite A
MA
Whited
Gregg
G
Bott
Richard
R
D000085:Acetates / Q000737:chemistry; D000217:Acyltransferases / Q000737:chemistry* / Q000235:genetics; D000438:Alcohols / Q000737:chemistry*; D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006861:Hydrogen Peroxide / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000235:genetics; D048448:Phenylcarbamates / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein; D014280:Triglycerides / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D000085:Acetates; D000438:Alcohols; D048448:Phenylcarbamates; D011409:Propylene Glycols; D011994:Recombinant Proteins; D014280:Triglycerides; D014867:Water; C007650:ethyl acetate; D006861:Hydrogen Peroxide; D000217:Acyltransferases; C048799:2,2-dimethyl-1,3-propanediol; C005830:tributyrin