Pectin is an excellent renewable feedstock that can be metabolized by Clostridium acetobutylicum, which is able to produce ethanol, butanol and acetone. The goal of this research is to increase butanol output through metabolic engineering; however, the proteins involved in the pectin utilization pathway have yet to be identified. Transcriptomic and qPCR analysis comparing growth on glucose and pectin identified genes induced during growth on pectin.  One of these genes encodes a putative glucuronyl hydrolase. The structure of this protein was solved to 1.5 � using x-ray crystallography and molecular replacement. The structure contains six a-hairpins, with two beta sheets and a small helix overlaying the end of the hairpins. The putative hydrolase has low sequence identity with the Bacillus subtillus rhamnogalacturonyl hydrolase Yter, but is structurally comparable with a RMSD of 1.5 �.  The active site of both proteins is similar, except the C. acetobutylicum UGL contains a loop that partially blocks the pocket and may be important for substrate specificity. C. acetobutylicum is not able to metabolize rhamnose, suggesting this protein is likely an unsaturated glucuronyl hydrolase that acts on digalacturonic acid, a byproduct of pectin degradation.

Clostridium acetobutylicum expresses a Yter like unsaturated glucuronyl hydrolase

247th National Meeting (2014)

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