| Abstract: | The gustatory responses of nine compounds, namely glycine, D-phenylalanine,D-tryptophan, cyanosuosan, magapame, sucrononate, campame, cyclamateand superaspartame, all known as sweet in man, were studiedin 41 species or subspecies of non-human primates, selectedamong Prosimii (Lemuridae and Lorisidae), Platyrrhini (Callitrichidaeand Cebidae) and Catarrhini (Cercopithecidae, Hylobatidae andPongidae). The first six compounds are generally sweet to allprimates, which implies that they interact with the primatesweetness receptors essentially through constant recognitionsites. Campame is sweet only to Cebidae and Catarrhini, cyclamateonly to Catarrhini, superaspartame principally to Callitrichidaeand Catarrhini, which implies that all these compounds interactwith the receptors partly through variable recognition sites.From the present work, from other previous results (where notablyit was observed that alitame is sweet to all primates, ampameonly to Prosimii and Catarrhini, and aspartame only to Catarrhini),and from the multipoint attachment (MPA) theory of sweetnessreception (as elaborated by Nofre and Tinti from a detailedstudy of structure-activity relationships of various sweetenersin man), it is inferred that the primate sweetness receptorsare very likely made up of eight recognition sites, of whichthe first, second, third, fourth, seventh and eighth are constant,and the fifth and sixth variable. From these results and fromthe MPA theory, it is also inferred that the recognition sitesof the primate sweetness receptors could be: Asp-1 or Glu-1,Lys-2, Asp-3 or Glu-3, Thr-4, X-5, X-6, Thr-7, Ser-8, wherethe variable recognition sites X-5 and X-6 would be: Ala-5 andAla-6 for Callitrichidae, Ser-5 and Ala-6 for Cebidae, Ala-5and Thr-6 for Prosimii, and Thr-5 and Thr-6 for Catarrhini.By using Tupaiidae (tree shrews) as a reference outgroup andby means of other structural and functional molecular considerations,it appears that Callitrichidae have retained the most primitivereceptor among the four types of primate receptors. The possibletaxonomic and phylogenetic implications of these findings arediscussed. Chem. Senses 21: 747–762, 1996. |
