Sulfur Amino Acid Metabolism in Hepatobiliary Disorders

Abstract

Sulfur amino acid metabolism was studied in patients with mild to severe forms of liver dysfunction and compared with that of healthy controls. Patients with mild liver dysfunction (for example, Gilbert's syndrome) had a normal sulfur amino acid metabolism. With increased inflammatory activity and cirrhosis (for example, chronic active hepatitis, alcohol-induced cirrhosis, and hepatic coma) a decreased ability to metabolize methionine (to cysteine, with cystathionine accumulation) and cysteine (to inorganic sulfate, with thiosulfate and N-acetylcysteine accumulation) was found. In contrast, transaminative metabolism of sulfur amino acids was preserved in patients with advanced forms of liver dysfunction, suggesting that transamination of sulfur amino acids is performed not only in the liver but also in extrahepatic tissues. Some implications of these findings are discussed.

Hypermethioninemias of genetic and non‐genetic origin: A review

“…As discussed by Morgan et al [1982], and exemplified by the extensive data in their article, typical (but not invariant) changes are increased concentrations of tyrosine and/or phenylalanine together with increased methionine, and decreases in valine, isoleucine, and leucine. In more serious liver disease mean cystathionine is above normal in urine [Mårtensson et al, 1992] and in serum [Look et al, 2000; Medici et al, 2010], and mean tHcy is slightly raised [Medici et al, 2010].…”

“…For GNMT , methionine synthase , BHMT , and CBS , mRNA concentrations were normal in only 4%, 0%, 11%, and 27%, respectively. Cystathionine gamma‐lyase activity may also be deficient [Mårtensson et al, 1992; Look et al, 2000; Medici et al, 2010]. Patients with severe loss of one type of mRNA tend to have severe losses of the other types [Avila et al, 2000], so that the abnormalities of sulfur amino acid metabolism in question may usually be explained by one‐or‐another combination of these enzyme activity deficiencies.…”

Protective Effects of S-Adenosylmethionine and Its Combinations With Taurine and/or Betaine Against Lipopolysaccharide or Polyinosinic-polycytidylic Acid-induced Acute Hepatotoxicity

“… 21 It has been shown that patients with liver disease have low serum cysteine, taurine and GSH concentration. 22 , 23 Nearly half of the cysteine is converted to GSH, and rest of that is converted into taurine and participates in protein synthesis depending on the need of the cells. 24 …”

Effects of S-Adenosylmethionine and Its Combinations With Taurine and/or Betaine on Glutathione Homeostasis in Ethanol-induced Acute Hepatotoxicity

“… 11 It has been reported that patients with liver injury have a low serum concentration of taurine, cysteine, and GSH. 12 , 13 Most of the cysteine is used for GSH synthesis and some is used for taurine and protein synthesis depending on the need of the cells. 14 It could be suggested that lowering the rate of catabolism of cysteine to taurine could preserve the cysteine supply for GSH synthesis.…”