The catalytic mechanism and unique low pH optimum of Caldicellulosiruptor bescii family 3 pectate lyase.

ABSTRACT: The unique active site of the Caldicellulosiruptor bescii family 3 pectate lyase (PL3) enzyme has been thoroughly characterized using a series of point mutations, X-ray crystallography, pK(a) calculations and biochemical assays. The X-ray structures of seven PL3 active-site mutants, five of them in complex with intact trigalacturonic acid, were solved and characterized structurally, biochemically and computationally. The results confirmed that Lys108 is the catalytic base, but there is no clear candidate for the catalytic acid. However, the reaction mechanism can also be explained by an antiperiplanar trans-elimination reaction, in which Lys108 abstracts a proton from the C5 atom without the help of simultaneous proton donation by an acidic residue. An acidified water molecule completes th

SUBMITTER: Alahuhta M 

PROVIDER: S-EPMC4556314 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature