ABSTRACT
Structure-activity relationship studies of amino acids in chemoreception of Marthasterias glacialis revealed that the substances inducing feeding are of low molecular weight and have two to six carbon atoms in molecule. Evidence is presented that the sulfhydryl group plays a rôle in response to L-cysteine. In L-cysteine methyl esters and glycine methyl esters the stimulatory effectiveness is not reduced. The primary carboxyl group most probably does not influence the receptors. On the contrary methylation of amino group in glycin increases its stimulatory power. Thus betaine serves as very effective feeding response releasing substance. Lactic acid and malic acid were found to have strong stimulatory properties for the feeding response.
