Multifunctional amino acid

Several dozens of aldolases have been identified so far in nature [23,24], and many of these enzymes are commercially available at a scale sufficient for preparative applications. Enzyme catalysis is more attractive for the synthesis and modification of biologically relevant classes of organic compounds that are typically complex, multifunctional, and water soluble. Typical examples are those structurally related to amino acids [5-10] or carbohydrates [25-28], which are difficult to prepare and to handle by conventional methods of chemical synthesis and mandate the laborious manipulation of protective groups. 

Amino acids are also readily available and relatively inexpensive chemical reagents for industrial use. The recent trend to develop products with multifunctional characteristics, for example as solvents or as fuel additives that act as inhibitors and dispersants - provides a good opportunity for utilization of amino acid esters. The unique multifunctional chemistry, environmental... 

Chimeric enzymes constructed fi"om two different angiosperms (Panax ginseng, Araliaceae, and Arabidopsis thaliana, Brassicaceae) yielded mixtures of triterpenoids, p-amirin and lupeol, at a composition depending on the particular chimera methyl scrambling was observed for lupeol only (Kushiro 1999). A few differences in the amino acids at the active site are responsible for these effects. This implies that the high variety of plant triterpenoids owes more to chimeric enzymes than product-specific triterpene synthases. It was proposed that these chimeric enzymes act as multifunctional triterpene synthases (Kushiro 1999). 

A detailed study of amino acid sequences and mechanistic similarities in various polyketide synthase (PKS) enzymes has led to two main types being distinguished. Type I enzymes consist of one or more large multifunctional proteins that possess a distinct active site for every enzyme-catalysed step. On the other hand, Type II enzymes are multienzyme complexes that carry out a single set of repeating activities. Like fatty acid synthases, PKSs catalyse the condensation of coenzyme A esters of simple carboxylic acids. However, the variability at each step in... 

Banko et al. [11] speculated that the putative dual-enzyme process was instead catalyzed by a single, multifunctional enzyme. Their data clearly showed that in cell-free extracts of C. acremonium the rate of ACV synthesis was significantly greater when the precursor amino acids were provided than it was when AC and valine were used as substrates for the reaction [11], Jensen and her coworkers [12] demonstrated a similar result using cell-free extracts of S. clavuli-gerus. 

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