Structural insight of two 4-Coumarate CoA ligase () isoforms in suggests targeted genetic manipulations could lead to better lignin extractability from the pulp.

4-Coumarate: coenzyme A ligase () is a key enzyme involved in the early steps of the monolignol biosynthetic pathway. It is hypothesized to modulate S and G monolignol content in the plant. Lignin removal is imperative to the paper industry and higher S/G ratio governs better extractability of lignin and economics of the pulping process. This background prompted us to predict 3D structure of two isoforms of in and evaluate their substrate preferences. The 3D structure of and protein were created by homology modeling and further refined by loop refinement. Molecular docking studies suggested differential substrate preferences of both the isoforms. preferred sinapic acid (- 4.91 kcal/mole), ferulic acid (- 4.84 kcal/mole), hydroxyferulic acid (- 4.72 kcal/mole), and caffeic acid (- 4.71 kcal/mole), in their decreasing order. Similarly, preferred caffeic acid (- 6.56 kcal/mole, 4 H bonds), hydroxyferulic acid (- 6.56 kcal/mole, 3 H bonds), and ferulic acid (- 6.32 kcal/mole) and sinapic acid (- 5.00 kcal/mole) in their decreasing order. Further, active site residues were identified in both the isoforms and in silico mutation and docking analysis was performed. Our analysis suggested that ASP228, TYR262, and PRO326 for and SER165, LYS247 and PRO315 for were important for their functional activity. Based on differential substrate preferences of the two isoforms, as a first step towards genetically modified having the desired phenotype, it can be proposed that over-expression of gene and/or down-regulation of gene could yield higher S/G ratio leading to better extractability of lignin.