H(+) + phenylglyoxylate = benzaldehyde + CO2 Binds 1 Ca(2+) ion per subunit. Binds 1 thiamine pyrophosphate per subunit. Binds 1 Mg(2+) ion per dimer. Aromatic compound metabolism; (R)-mandelate degradation; benzoate from (R)-mandelate: step 3/4. Homotetramer. Belongs to the TPP enzyme family.