Production of Tyrosine and Histidine Decarboxylase by Dairy-Related Bacteria.

Manometric and radiometric procedures were used to determine the ability of 38 dairy-related bacteria and four commercial starter preparations to produce tyrosine and histidine decarboxylase. All of the cultures had slight ability to cause release of CO from carboxyl C-tyrosine and most released CO from labeled histidine; however, because of inherent errors of the assay in detecting low levels of specific decarboxylase activity, the CO release was not considered positive for specific decarboxylase activity unless the results were verified by the manometric technique. One strain of Streptococcus lactis , a Micrococcus luteus strain, and two Leuconostoc cremoris strains had active tyrosine decarboxylase systems. Only Clostridium perfringens and an Escherichia coli strain were found to produce histidine decarboxylase. None of the commercial starter cultures produced the enzymes. It was not determined whether tyramine or histamine was produced by the nonspecific decarboxylase activity.