The faeA gene from Aspergillus niger encoding a feruloyl esterase with activity on xylan and pectin is subject to a complex system of regulation

Cinnamoyl esterases play a role in the complete degradation of plant cell w all polysaccharides (xylan and pectin) by micro-organisms. The induction an d repression of a gene encoding a feruloyl esterase from Aspergillus niger (faeA), which encodes an enzyme with activity on both xylan and pectin, has been studied using activity measurements and Northern analysis. The gene w as expressed on xylan as well as on pectin. The expression on xylan was muc h higher than on pectin, suggesting that xylan is the preferred substrate. Northern analysis demonstrated that the gene is expressed on xylose and fer ulic acid. This indicates the presence of two systems for induction, a xyla n/xylose specific system (XlnR) and a ferulic acid specific system. Additio n of ferulic acid enhanced the induction on xylan, indicating a positive in teraction between the two inducing systems. Glucose represses the induction of faeA on xylose and ferulic acid. A compa rison of the expression of faeA in the A niger wild-type strain and in a ca rbon catabolite derepressed mutant of A niger demonstrated that repression of faeA expression is indeed mediated by CreA. (C) 1999 Society of Chemical Industry.