AMINO-ACID-SEQUENCE OF THE MINOR ISOMORPH OF THE CRUSTACEAN HYPERGLYCEMIC HORMONE (CHH-II) OF THE MEXICAN CRAYFISH PROCAMBARUS-BOUVIERI (ORTMANN) - PRESENCE OF A D-AMINO-ACID

The primary structure of the neurohormone crustacean hyperglycemic hor mone (CHH-II) was determined by means of enzymatic digestions, manual Edman degradation, and mass spectrometry. CHH-II is a 72 residue pepti de (molecular mass 8388 Dal, with six cysteines forming three disulfid e bridges that connect residues 7-43, 23-39, and 26-52. The peptide ha s bloc):ed N- and C-termini, and lacks tryptophan, histidine, and meth ionine. The CHH-I and CHH-II of Procambarus bouvieri have identical se quences and elicit levels of hyperglycemia that are not distinguishabl e. The difference between the two isomorphs consists in a posttranslat ional modifcation of a L-Phe in CHH-I to a D-Phe in CHH-II at the thir d position from the N-terminus.