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

Abstract

The site of phosphorylation of phenylalanine ammonia-lyase (PAL) has been identified as a threonine residue. A Ca 2+ -stimulated protein kinase of approximately 55 kDa has been partially purified from elicited cells. The kinase can phosphorylate a synthetic peptide derived from PAL and a recombinant poplar PAL. PAL phosphorylation was associated with a decrease in V max in agreement with the suggestion that protein phosphorylation is involved in marking PAL subunits for turnover. The phosphorylation site in French bean PAL is most likely Thr 545 in the sequence VAKRTLTT (539^546). Conservation of the phosphorylation site in PAL from diverse species suggests that phosphorylation of PAL may be a ubiquitous regulatory mechanism in higher plants.z 1999 Federation of European Biochemical Societies.

Phosphorylation is an on/off switch for 5-hydroxyconiferaldehyde O -methyltransferase activity in poplar monolignol biosynthesis

“…Phosphorylation and CIAP treatments did not alter the PAL activity in SDX compared with the control (Fig. 5B), consistent with the observation that recombinant PAL catalytic efficiency (V max /K m ) was unaffected by phosphorylation (19). Having confirmed the phosphorylation-mediated inhibition of PtrAldOMT2 activity, we next focused on the functional roles of the individual PtrAldOMT2 phosphorylation sites.…”

“…PAL catalytic efficiency was unaffected by this phosphorylation (19). Instead, the phosphorylation was predicted to mark particular PAL subunits for turnover or to target them for specific subcellular compartments (19,20). No evidence of protein phosphorylation was presented for the remaining monolignol biosynthetic enzymes.…”

“…Subsequently a synthetic peptide of PAL and a recombinant poplar PAL were shown to be phosphorylated by protein fractions of elicitor-induced French bean cell suspension cultures (19). The same synthetic peptide and poplar recombinant PAL was later shown to be phosphorylated by an Arabidopsis thaliana calcium-dependent kinase (AtCPK1) (20,21).…”

“…The same synthetic peptide and poplar recombinant PAL was later shown to be phosphorylated by an Arabidopsis thaliana calcium-dependent kinase (AtCPK1) (20,21). PAL catalytic efficiency was unaffected by this phosphorylation (19). Instead, the phosphorylation was predicted to mark particular PAL subunits for turnover or to target them for specific subcellular compartments (19,20).…”

Induction of anthraquinone biosynthesis in Rubia cordifolia cells by heterologous expression of a calcium‐dependent protein kinase gene

“…Identification of specific CDPK isoforms in French bean and Arabidopsis that could phosphorylate phenylalanine ammonia lyase (PAL), a key enzyme in defense responses, provided an apparent link between secondary metabolism and stress perception via CDPK (Allwood et al, 1999(Allwood et al, , 2002Cheng et al, 2001). To our knowledge, the effect of heterologous expression of CDPK genes on secondary metabolism in plants or in plant cell cultures has not yet been studied.…”