ζ-Crystallin displays strong selectivity for salicylic acid over aspirin

• Published in: Biochemical and biophysical research communications Vol. 293; no. 1; pp. 440 - 445
• Main Author: Bazzi, Mohammad D
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.04.2002
• Subjects: Animals; Aspirin; Aspirin - metabolism; Camelus; Cataract; Crystallins - chemistry; Crystallins - metabolism; Kinetics; NADP - metabolism; Protein fluorescence; Salicylate-binding proteins; Salicylic Acid - metabolism; Spectrometry, Fluorescence; α-Crystallin; ζ-Crystallin; α-Crystallin; Aspirin; Salicylate-binding proteins; Cataract; Protein fluorescence; ζ-Crystallin
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(02)00248-6

Interaction of camel lens ζ-crystallin with aspirin was investigated by activity and fluorescence measurements. Aspirin minimally inhibited the oxidoreductase activity of the enzyme and weakly quenched its fluorescence. However, significant fluorescence quenching of ζ-crystallin coincided with the appearance of a fluorescence signal characteristic of salicylic acid thereby raising the possibility that salicylic acid might have been the moiety responsible for inhibition and fluorescence quenching. Direct fluorescence measurements showed that ζ-crystallin had a much higher affinity for salicylic acid than aspirin ( K i of about 24 μM for salicylic acid versus 630 μM for aspirin). Salicylic acid was also far more effective in inhibiting ζ-crystallin than aspirin ( K i values were 23 μM versus 820 μM , respectively). Inhibition kinetics suggested that salicylic acid interacted with ζ-crystallin via a binding site that was distinct from that of NADPH. Salicylic acid also interacted with and quenched the fluorescence of camel lens α-crystallin suggesting a general mode of interaction with lens proteins. Within the normal therapeutic concentrations of salicylic acid or aspirin, only crystallin–salicylic acid interactions might be significant. These results showed that camel lens ζ- and α-crystallin exhibited remarkable selectivity for salicylic acid over aspirin, and thus, could be considered as salicylate-binding proteins.