The phenylalanine ammonia lyase(PAL) is the one of the best studied enzyme concerned with secondary metabolism in plants.This enzyme is discovered by Koukol and Conn in 1961.It is a key enzyme of plant and fungi phenylpropanoid metabolism and it is usually encoded by a multigene family involved in the biosynthesis of a wide variety of secondary metabolites such as flavanoids,furanocumarin,phytoalexinsand cell wall components,UV protechtants which are important for the normal growth of plants and response to enviromental stress.

It catalyses the elimination of ammonia from L-phenylalanine and producing trans-cinnamate in the first step of phenylpropanoid pathway.This pathway plays important role in development of fruit colour and flavour.PAL plays in crucial role in biosynthesis of cucumarin in turmeric.The other names of this enzyme are tyrase,phenylalanine deaminase and phenylalanine ammonium-lyase.This enzyme is located inthe cytoplasm,and was possibly membrane associated(Shaw et al., 1990).

           This enzyme is present in all plants and also in some bacteria,yeast and fungi.  Information on different aspects of this enzyme is available in different websites. Understanding the molecular basis of this PAL enzyme will be helpful to pursue the research work.

Inhibitors:
         Cinnamic acid is an effective inhibitor and (1-Amino-2-phenylethyl) phosphonic acid(APEP),(1-Amino-2-phenyl-ethyl) phosphonous acid(APEPi),alpha-aminooxy-beta-phenylpropionic acid(AOPP)(karl godeke,1976) and several other phenylalanine analogues are potent inhibitors of PAL in vitro and in vivo.

Active site
        This enzyme has a dehydroalanyl residue at the active site and in this respect resembles histidine ammonia lyase(Givot et al., 1969).So these two enzymes are functionally and structurally related.they are the only enzymes ,which are known to have modified amino acid dehroalanine(DHA) in their active site.A serine residue has been shown to be the precursor of this essential electrophilic moiety.The region around this active site is highly conserved.The consensus patternof this active site is G-[STG]-[LIVM]-[STG]-[AC]-S-G-[DH]-L-x-P-L-[SA]-x(2)-[SA].

Transmembrane region
       This PAL enzyme has transmembrane region,which revealed that it could pass through the membrane.The region is present in the position between 240-280 and the aminoacid sequence starts with GLALVNGTSVGSGMASMVLF,and these are mostly hydrophobic in nature.In PAL enzymes this leucine could be changed as Isoleucine,serine could be changed as Alanine, and methionine could be changed as leucine.

Primers
       The conserved region were found as GTITASGDLVPLSYIA(Taylor et al.,1994) HGGNFQG and EQHNQDV in the position of 180,380,470 respectively.Degenerate Primers were designed for this sequence.This will be helpful in the sequencing of PAL in spices.The total size of the gene is approximately 2150.The designed primers are
                                                                  POSITION

GTITASGDLVPLSYIA   - 5'   NGGNACNATHACNGC     3'         570   
HGGNFQG                        - 5'    RGGNGGNAARTTRCA      3'       1163
EQHNQDV                        - 5'    RCAYAAYCARGAYGT      3'       1428