Cg10062 is a cis-3-chloroacrylic acid dehalogenase (cis-CaaD) homologue from Corynebacterium glutamicum with unknown function and no genomic context.  Cg10062 shares 34% sequence identity (and 53% similarity) with cis-CaaD including six residues (Pro-1, His-28, Arg-70, Arg-73, Tyr-103, Glu-114) implicated as key players in the cis-CaaD mechanism.  Like cis-CaaD, Cg10062 functions as a hydratase:  it converts 2-oxo-3-pentynoate to acetopyruvate and processes 3-bromopropiolate to a species that inactivates the enzyme.  However, Cg10062 is a poor cis-CaaD:  it has much lower catalytic efficiency and lacks stereospecificity.  The parallels between cis-CaaD and Cg10062 coupled with the absence of a robust cis-CaaD activity and isomer specificity in Cg10062 indicate that a fully functional cis-CaaD requires elements beyond the core set.  Kinetic, mutagenesis, and structural analysis suggest that Cg10062 could be a few mutations away from a highly specific and efficient cis-CaaD.  As such, Cg10062 could be representative of a progenitor for cis-CaaD.  (Supported by NIH GM 65324 and the Welch Foundation F-1334).