Co-Authors:
Bryant, B.P., Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, United States
Harpaz, S., Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, United States
Brand, J.G., Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, United States
Abstract:
To characterize the molecular/structural requirements for activation or antagonism of the arginine taste pathways in catfish, Ictalurus punctatus, structure/activity studies were performed using integrated multi-unit responses and cross-adaptation. Of all the guanidinium-containing compounds tested, only L-arginine, L-α-amino-β-guanidino propionic acid (L-AGPA) and L-arginine methyl and ethyl esters were strong stimuli. Results of functional group substitutions and modifications of the L-arginine parent molecule indicated that: (i) stereospecificity was observed with D-arginine being a much less effective stimulus than L-arginine; (ii) an L-amino group must be present and unblocked (α-chloro-guanidino-N-valeric acid N-acetyl L-arginine were weak or inactive stimuli); (iii) a free carboxylic acid group was not necessary for activity; (iv) the distance between the anomeric carbon and the guanidinium group was not critical (L-AGPA, having two methylene groups less than L-arginine was a moderately strong stimulus as was L-canavanine) and (v) modification or substitution of the guanidinium group by other basic groups including amine, methyl or dimethylamine or by an isostere (ureido) resulted in loss of stimulatory ability. In general, those stimuli and analogs that were good cross-adapters of L-arginine stimulation were also good competitors for L-[ 3H]arginine binding to a partial membrane fraction (P2) from catfish taste epithelium. On the other hand, compounds that were poor cross-adapting stimuli were also poor binding competitors. While D-arginine was a poor stimulus, it did cross-adapt L-arginine and competed well with L-[ 3H]arginine for binding to fraction P2.
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מונוכרום
הדגשת קישורים
חסימת אנימציה
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