4-COUMARATE-COENZYME-A LIGASE FROM LOBLOLLY-PINE XYLEM - ISOLATION, CHARACTERIZATION, AND COMPLEMENTARY-DNA CLONING

4-Coumarate:CoA ligase (4CL, EC 6.2.1.12) was purified from differenti ating xylem of loblolly pine (Pines taeda L.). The pine enzyme had an apparent molecular mass of 64 kD and was similar in size and kinetic p roperties to 4CL isolated from Norway spruce. The pine enzyme used 4-c oumaric acid, caffeic acid, ferulic acid, and cinnamic acid as substra tes but had no detectable activity using sinapic acid. 4CL was inhibit ed by naringenin and coniferin, products of phenylpropanoid metabolism . Although the lignin composition in compression wood is higher in p-h ydroxyphenyl units than lignin from normal wood, there was no evidence for a different form of 4CL enzyme in differentiating xylem that was forming compression wood. cDNA clones for 4CL were obtained from a xyl em expression library. The cDNA sequences matched pine xylem 4CL prote in sequences and showed 60 to 66% DNA sequence identity with 4CL seque nces from herbaceous angiosperms. There were two classes of cDNA obtai ned from pine xylem, and the genetic analysis showed that they were pr oducts of a single gene.