p-Cresol sulfate is a microbial metabolite that is found in urine and likely derives from secondary metabolism of p-cresol. It appears to be elevated in the urine of individuals with progressive multiple sclerosis. p-Cresol sulfate is the major component of urinary MBPLM (myelin basic protein-like material). p-Cresol sulfate is a small protein-bound molecule that is poorly cleared with dialysis. It has been identified as a uremic toxin according to the European Uremic Toxin Working Group. Uremic toxins include other low-molecular-weight compounds such as indoxyl sulfate, 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid, and asymmetric dimethylarginine. It has also been linked to cardiovascular disease and oxidative injury. Higher levels are associated with overgrowth of intestinal bacteria from Clostridia species, including C. difficile. p-Cresol is generated by the partial breakdown of tyrosine and phenylalanine by a wide range of intestinal obligate or facultative anaerobes, including the genera Bacteroides, Lactobacillus, Enterobacter, Bifidobacterium, and especially Clostridium. The reversible reaction of l-tyrosine with 2-oxoglutarate in 4-hydroxyphenylpyruvate and L-glutamate is catalysed by tyrosine transaminase (EC 2.6.1.5.) or by aromatic-amino-acid transaminase (EC 2.6.1.57.) To a small extent, 4-hydroxyphenylpyruvate and ammonia can also be formed by the enzyme phenylalanine dehydrogenase (EC 1.4.1.20.) from l-tyrosine. 4-Hydroxyphenylpyruvate is the precursor of 4-hydroxyphenylacetate, catalysed by p-hydroxyphenylpyruvate oxidase (EC 1.2.3.13.), and can subsequently lead to the formation of p-cresol by p-hydroxyphenylacetate decarboxylase. In the gut mucosa and in the liver, the majority of p-cresol will be conjugated into the uremic toxin p-cresyl sulfate by aryl sulfotransferases (EC 2.8.2.1.).

Metabolism and Physiological Effects of p-Cresol sulphate References