The present invention refers to an enzyme consisting of a fusion protein particularly useful as shown through-out the present invention for carrying out the carbon-carbon bond-forming reaction known as the aldol Reaction, preferably for carrying out an aldol reaction by using aldehydes as substrates and preferably pyruvate or a salt thereof, for producing hydroxyketoacids. Said enzyme is made by binding an aldolase to a maltose binding protein. The enzymes display full activity under “highly denaturing” substrate loadings (aldehydes, >1 M).