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COMPARATIVE ACTIVITIES OF PHENYLALANINE AMMONIA-LYASE AND TYROSINE AMMONIA-LYASE AND PHENOLIC COMPOUNDS ACCUMULATED IN CASSAVA ELICITED CELL
Plants respond to attack by pathogens by initiating a change in
cellular metabolism, leading to synthesis of antifungal proteins,
production of phytoalexins and/or accumulation of phenolic compounds,
namely lignins and salicylic. Lignins reinforce pectocellulosic cell
walls and limit the invasion of plant tissues by pathogens; while
salicylic acid plays a role in signals plant defense against pathogens.
The objective of this study was to evaluate the activities of
phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) and tyrosine
ammonia-lyase (TAL, EC 4.3.1.5); and to determine the level of their
involvement in the biosynthetic pathway of these phenylpropanoids in
cells of cassava ( Manihot esculenta Crantz, cv Yac\ue9) elicited
with salicylic acid (SA). PAL and TAL activities were demonstrated in
crude extract enzyme. PAL activity was 9.8 times greater than that of
TAL in the pellet obtained with 20% (w/v) ammonium sulphate. In the
extract treated with Dowex 2 (cationic), TAL activity was 36.7 times
greater than that of PAL. pH and temperature optima of PAL (8; 40\ub0
C) differed from those of TAL (8.5; 30\ub0 C). In the presence of SA,
PAL and TAL activities were respectively maximum 24 and 72 hr after
inoculation. TAL activity and induced phenols were much higher than
PAL. PAL and TAL activities were optimised respectively, by 75 and 100
\u3bcM of SA. The synthesis of phenolic compounds was concomitant with
enzymes stimulation. These results show that PAL is different from TAL
and the two enzymes are involved in the biosynthetic pathway of
phenylpropanoids in cassava.Les plantes r\ue9pondent \ue0 l\u2019attaque des pathog\ue8nes
par l\u2019initiation d\u2019un changement du m\ue9tabolisme
cellulaire, conduisant \ue0 la synth\ue8se des prot\ue9ines
antifongiques, la production des phytoalexines et/ou
l\u2019accumulation des compos\ue9s ph\ue9noliques appel\ue9s
lignines et salicyliques. Les lignines renforcent les membranes
cellulaires p\ue9ctocellulosiques et limitent l\u2019invasion des
tissues des plantes par les pathog\ue8nes, alors que l\u2019acide
salicylique joue un r\uf4le dans les signaux de d\ue9fense des
plantes contre les pathog\ue8nes. Cette \ue9tude avait pour
objectif d\u2019\ue9valuer les activit\ue9s du phenylalanine
ammonia-lyase (PAL, EC 4.3.1.5) et du tyrosine ammonia-lyase (TAL, EC
4.3.1.5) ainsi que de d\ue9terminer le niveau de leur implication
dans la voie biosynth\ue9tique de ces ph\ue9nylpropanoides dans les
cellules de manioc ( Manihot esculenta Crantz, cv Yac\ue9) dues
\ue0 l\u2019acide salicylic. Les activit\ue9s PAL et TAL
\ue9taient d\ue9montr\ue9es dans un extract de base
d\u2019enzyme. L\u2019activit\ue9 PAL \ue9tait 9.8 fois plus
\ue9lev\ue9e que celle de TAL dans la boulette obtenue du sulfate
d\u2019ammonium (w/v) 20%. Dans l\u2019extract trait\ue9 avec Dowex
2 (cationique), l\u2019activit\ue9 TAL \ue9tait 36.7 fois plus
\ue9lev\ue9e que celle du PAL. Le pH et la temp\ue9rature optima
de PAL (8; 40\ub0 C) diff\ue9raient de ceux du TAL (8.5; 30\ub0
C). En pr\ue9sence de l\u2019acide salicylique, les activit\ue9s
PAL et TAL \ue9taient respectivement maximum \ue0 24 et 72 heures
apr\ue8s inoculation. L\u2019activit\ue9 TAL ainsi que les
ph\ue9nols induits \ue9taient plus \ue9lev\ue9s que PAL. Les
activit\ue9s PAL et TAL \ue9taient plus optimis\ue9es
respectivement par 75 et 100 \u3bcM de l\u2019acide salicylique. La
synth\ue8se des compos\ue9s ph\ue9noliques \ue9tait
concomitante avec la stimulation enzymatiques. Ces r\ue9sultats
montrent que PAL est diff\ue9rent de TAL et les deux enzymes sont
impliqu\ue9s dans la voie biosynth\ue9tique des
ph\ue9nylpropano\ubfdes dans le manioc