Oxaloacetate decarboxylase or OAD functions as a Na pump in anaerobic bacteria. It is a membrane protein consisting of three subunits, α, β and γ with the α subunit containing the carboxylase activity.

Oxaloacetate Decarboxylase from Pseudomonas sp. has been used in the digestion of the low molecular weight (LMW) human milk fraction (5kF fraction) and as a positive control for deciphering C. thermocellum oxaloacetate decarboxylase activity.

Oxaloacetate decarboxylase has been used in a study to assess turnover and accessibility of a reentrant loop of the Na(+)-glutamate transporter GltS. It has also been used in a study to investigate fermentation and metabolic characteristics of Gluconacetobacter oboediens for different carbon sources.

Oxaloacetate Decarboxylase catalyzes the decarboxylation of oxaloacetate and requires manganese and magnesium for its activity. It is associated with a wide vareity of Gram-negative bacteria.

One unit will convert 1.0 μmole of oxalacetate to pyruvate and CO₂ per min at pH 8.0 at 25 °C.