L-Tyrosine decarboxylase from Streptococcus faecalis has been used in a study to isolate and identify the carbonyl-active site of diamine oxidase by gas chromatographic mass spectrometry. L-Tyrosine decarboxylase from Streptococcus faecalis has also been used in a study to investigate the adsorption of Streptococcus faecalis on diatomite carriers for use in biotransformations.