Serine carboxypeptidase-like acyltransferases.

Area of Science:

• Plant biochemistry
• Molecular evolution
• Enzymology

Background:

• Plant secondary metabolism involves ester formation via acyltransferases.
• Some acyltransferases utilize 1-O-beta-acetal esters as acyl donors, differing from typical coenzyme A thioesters.
• These enzymes are homologous to serine carboxypeptidase-type hydrolases, termed serine carboxypeptidase-like (SCPL) acyltransferases.

Purpose of the Study:

• To investigate the evolutionary recruitment and functional adaptation of SCPL proteins in plants.
• To understand the molecular basis for SCPL acyltransferases' catalytic activity.
• To identify plant SCPL proteins involved in acyl transfer reactions.

Main Methods:

• Molecular data analysis to determine homology between acyltransferases and hydrolases.
• Sequence comparison to cluster Arabidopsis SCPL proteins with known SCPL acyltransferases.
• Structural elucidation of related bacterial thioesterase domains to infer mechanisms of altered activity.

Main Results:

• SCPL acyltransferases are evolutionarily recruited from serine carboxypeptidases, adapted for acyl transfer.
• These enzymes belong to the alpha/beta hydrolase class, utilizing a catalytic triad.
• Bacterial thioesterase domains show altered activity favoring transfer over hydrolysis due to water exclusion and oxyanion hole distortion.
• A significant number of Arabidopsis SCPL proteins cluster with known SCPL acyltransferases, indicating widespread co-option for acyl transfer.

Conclusions:

• SCPL acyltransferases represent a key system for studying functional adaptation and molecular evolution in plant genes.
• The findings highlight the plasticity of the SCPL protein family in adopting acyl transferase functions.
• This research expands our understanding of plant secondary metabolism and enzyme evolution.