Novel type III polyketide synthases from Aloe arborescens.

Aloe arborescens is a medicinal plant rich in aromatic polyketides, such as pharmaceutically important aloenin (hexaketide), aloesin (heptaketide) and barbaloin (octaketide). Three novel type III polyketide synthases (PKS3, PKS4 and PKS5) were cloned and sequenced from the aloe plant by cDNA library screening. The enzymes share 85-96% amino acid sequence identity with the previously reported pentaketide chromone synthase and octaketide synthase.

Structure function analysis of novel type III polyketide synthases from Arabidopsis thaliana.

The genome sequencing project revealed presence of two active chalcone synthase (CHS) homologues (At1g02050 and At4g34850) in the model plant Arabidopsis thaliana. We report herein the two genes encode closely related novel plant-specific type III polyketide synthases (PKSs) that produces long-chain alkyl alpha-pyrones. PKS-A (At1g02050) and PKS-B (At4g34850) share significantly low amino acid sequence identity (20-40%) with other type III PKSs, and the phylogenetic tree analysis revealed that they form a separate cluster located closely to those of bacterial type III PKSs.

Cloning and functional analysis of a novel aldo-keto reductase from Aloe arborescens.

A novel aldo-keto reductase (AKR) was cloned and sequenced from roots of Aloe arborescens by a combination of RT-PCR using degenerate primers based on the conserved sequences of plant polyketide reductases (PKRs) and cDNA library screening by oligonucleotide hybridization. A. arborescens AKR share similarities with known plant AKRs (40-66% amino acid sequence identity), maintaining most of the active-site residues conserved in the AKR superfamily enzymes.