The Broad-specificity, Membrane-bound Lactate Dehydrogenase of Neisseria gonorrhoeae: Ties to Aromatic Metabolism

1 Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA 2 Department of Laboratory Medicine, Hamilton General Hospital, 237 Barton Street East, Hamilton, Ontario, Canada L8L 2X2 ABSTRACT Neisseria gonorrhoeae can convert phenyllactate (PL) to phenylalanine and 4-hydroxyphenyllactate (HPL) to tyrosine. This was demonstrated by nutritional and physiological approaches. The enzymic basis for this unusual ability was shown to be the broad specificity of a particulate, unidirectional, pyridine-nucleotide-independent lactate dehydrogenase. This enzyme, denoted [iLDH], has been implicated in a pathogenic mechanism whereby host-derived lactate is linked to increased gonococcal oxygen consumption and electron transport. A similar role for HPL, a metabolite available in human host tissues, may provide a selective basis to explain evolution of broadened [iLDH] specificity in Neisseria . The interplay between aromatic metabolism and [iLDH] suggests new approaches for manipulating the host-pathogen relationship.