Paper accepted: “A specific amino acid residue in the catalytic site of dandelion polyphenol oxidases acts as 'selector' for substrate specificity”
Sarah Prexler and her co-authors’ paper on the identification of an amino residue in plant polyphenol oxidases that co-determines their substrate specificity has been accepted today in the journal “Plant Molecular Biology”. This paper is the latest from our young researchers group on plant PPOs which is still under remote supervision by Mareike Dirks-Hofmeister, our former BSc and MSc student, doctoral and post-doctoral researcher who succeeded in the first heterologous expression of these ubiquitous genes in E. coli. This allows us to perform site-directed mutagenesis to test some of the hypotheses put forward in the past to explain the enzyme’s mode of action, and to develop and test new ones. We had previously defined two subclasses of plant PPOs which differ in structure, i.e. amino acid sequence, and function, i.e. substrate preference. Together, Sarah Prexler and our bioinformatics post-doc Ratna Singh now showed that a crucially positioned hydrophobic isoleucine in group 1 PPOs and a positively charged arginine in group 2 PPOs close to one of the copper binding sites is responsible for the different substrate preferences of the enzymes. As usual, the PPO group heads the way in our engineering efforts to understand structure-function relationships of enzymes.