Identification of catalytically distinct arylalkylamine N-acetyltransferase splicoforms from Tribolium castaneum.

The assumption that structural or sequential homology between enzymes implies functional homology is a common misconception. Through in-depth structural and kinetic analysis, we are now beginning to understand the minute differences in primary structure that can alter the function of an enzyme completely. Alternative splicing is one method for which the activity of an enzyme can be controlled, simply by altering its length. Arylalkylamine N-acetyltransferase A (AANATA) in D. melanogaster, which catalyzes the N-acetylation of biogenic amines, has multiple splicoforms - alternatively spliced enzyme isoforms - with differing tissue distribution. As demonstrated here, AANAT1 from Tribolium castaneum is another such enzyme with multiple splicoforms. A screening assay was developed and utilized to determine that, despite only a 35 amino acid truncation, the shortened form of TcAANAT1 is a more active form of the enzyme. This implies regulation of enzyme metabolic activity via alternative splicing.