Oxalate oxidoreductases (EC 1.2.7.10) (OOR) are a relatively recently discovered group of enzymes that break down oxalate, a problematic molecule nutritionally. The first one to have been characterized has the systematic name oxalate:ferredoxin oxidoreductase.^[1][2] This enzyme catalyses the following chemical reaction:

oxalate + oxidized ferredoxin ${\displaystyle \rightleftharpoons }$ 2 CO₂ + reduced ferredoxin

This enzyme contains thiamine diphosphate and [4Fe-4S] clusters.^{[further explanation needed]}

Another OOR from acetogenic bacteria, a thiamine pyrophosphate (TPP)-dependent OOR, had its mechanism of action decoded step by step under X-ray crystallography to rather simplistically (one-carbon) split oxalate, producing low-potential electrons and CO₂.^[3]