Carnosine in olfaction : Proton magnetic resonance spectral evidence for tissue-specific carnosine binding sites.

The amount and specificity of binding ofL-carnosine (β-alanyl-L-histidine) by crude soluble and particulate fractions of several tissues were investigated with proton magnetic resonance ((1)HMR) spectrometry. It was found that the particulate fraction of only nasal olfactory mucosa exhibited a specific binding requiring a particular orientation of the carnosine molecule relative to the binding site. This suggests that whatever role carnosine may play in olfaction is expressed within the nasal olfactory mucosa rather than elsewhere in the olfactory pathway. Possible binding of carnosine to carnosinase was observed in the soluble fractions of nasal olfactory mucosa and kidney. However, the bulk of the carnosine present in the nasal olfactory mucosa in vivo probably is not bound within the cells of this tissue as a complex with soluble protein. These observations are of interest because the nasal olfactory mucosa is the neural tissue that has the highest activities of the enzymes catalyzing the synthesis and degradation of carnosine.The results of this investigation indicate that(1)HMR spectrometry will prove useful for the measurement of transmitter/receptor recognition. The significance of these results in the general context of measurement of "specific" binding interactions by biological samples is discussed, and a basic description of the application of(1)HMR spectrometry to these measurements is presented.