Reactions of aqueous chlorine in vitro in stomach fluid from the rat: chlorination of tyrosine.
Aqueous chlorine reacts with tyrosine to form ring-chlorinated products. Ring substitution occurs at Cl:tyrosine mole ratios greater than 1. Because the nitrogen function of amides is much less reactive than that of amines, the aromatic ring of N-acetyltyrosine is chlorinated at chlorine:substrate mole ratios less than 1. When an aqueous solution of the gastric protein pepsin was chlorinated (37 degrees C, 45 min), tyrosine residues were chlorinated at pH 2 but not at pH 8. The carbohydrate, protein, and chloride concentrations in stomach fluid from fasted rats were determined. When varying concentrations of aqueous chlorine (20-180 mg/L Cl2) were added to the stomach fluid at pH 2, tyrosine residues were mono- and dichlorinated on the aromatic ring. The amount of mono- to dichlorination products varied with the concentration of aqueous chlorine. A mechanism is proposed. The implications for toxicological studies involving chlorinated drinking water are discussed.
Nickelsen
M G
MG
Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529-0126.
Nweke
A
A
Scully
F E
FE
Ringhand
H P
HP
D000818:Animals; D002713:Chlorine / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D005750:Gastric Juice / Q000378:metabolism*; D010434:Pepsin A / Q000378:metabolism*; D051381:Rats; D012996:Solutions; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism*; D014867:Water
D012996:Solutions; D014867:Water; D014443:Tyrosine; D002713:Chlorine; C025787:N-acetyltyrosine; D010434:Pepsin A