Phosphorylation of phenylalanine ammonia-lyase: evidence for a novel protein kinase and identification of the phosphorylated residue

The site of phosphorylation of phenylalanine ammonia-lyase (PAL) has been i dentified as a threonine residue, A Ca2+-stimulated protein kinase of appro ximately 55 kDa has been partially purified from elicited cells, The kinase can phosphorylate a synthetic peptide derived from PAL and a recombinant p oplar PAL. PAL phosphorylation,vas associated,vith a decrease in V-max in a greement with the suggestion that protein phosphorylation is involved in ma rking PAL subunits for turnover, The phosphorylation site in French bean PA L is most likely Thr(545) in the sequence VAKRTLTT (539-546), Conservation of the phosphorylation site in PAL from diverse species suggests that phosp horylation of PAL may be a ubiquitous regulatory mechanism in higher plants , (C) 1999 Federation of European Biochemical Societies.