One of five 2-oxo acid decarboxylases (PDC1, PDC5, PDC6, ARO10, and THI3) involved in amino acid catabolism. The enzyme catalyzes the decarboxylation of amino acids, which, in a first step, have been transaminated to the corresponding 2-oxo acids (alpha-keto-acids). In a third step, the resulting aldehydes are reduced to alcohols, collectively referred to as fusel oils or alcohols. Its preferred substrates are the transaminated amino acids derived from phenylalanine (phenylpyruvate), tryptophan (3-(indol-3-yl)pyruvate), and probably tyrosine (4-hydroxyphenylpyruvate), but also isoleucine ((3S)-3-methyl-2-oxopentanoate, also alpha-keto-beta-methylvalerate) and methionine (4-methylthio-2-oxobutanoate), whereas transaminated leucine (4-methyl-2-oxopentanoate, also alpha-keto-isocaproate) is a low efficiency substrate and transaminated valine and pyruvate are no substrates. In analogy to the pyruvate decarboxylases the enzyme may in a side-reaction catalyze condensation (or carboligation) reactions leading to the formation of 2-hydroxy ketone, collectively called acyloins. 4-methyl-2-oxopentanoate + H(+) = 3-methylbutanal + CO2 (S)-3-methyl-2-oxopentanoate + H(+) = 2-methylbutanal + CO2 H(+) + indole-3-pyruvate = CO2 + indole-3-acetaldehyde 3-phenylpyruvate + H(+) = 2-phenylacetaldehyde + CO2 4-methylsulfanyl-2-oxobutanoate + H(+) = 3-methylsulfanylpropanal + CO2 3-(4-hydroxyphenyl)pyruvate + H(+) = (4-hydroxyphenyl)acetaldehyde + CO2 Binds 1 Mg(2+) per subunit. Binds 1 thiamine pyrophosphate per subunit. Optimum pH is 6.5-7.0. Amino-acid degradation; Ehrlich pathway. Expression is induced by the presence of aromatic amino acids and the lack of preferred nitrogen sources (e.g. ammonia, glutamine) and requires the transcription activator ARO80. Fusel oils are important flavor and aroma compounds in yeast-fermented products contributing to the quality of beverages and food. In low concentration they are generally desirable, whereas high concentrations may spoil the product. By adjusting growth conditions and substrate their production is sought to be influenced. Phenylethanol, having a rose-like aroma, is an important fragrance in the cosmetic industry and can be produced by fermentation. Present with 6560 molecules/cell in log phase SD medium. Belongs to the TPP enzyme family.