Octopamine in invertebrates.

Neuropeptides in the nervous system of Drosophila and other insects: multiple roles as neuromodulators and neurohormones.

Drosophila neuropeptides in regulation of physiology and behavior

Exposure of food proteins to certain processing conditions induces two major chemical changes:  racemization of all l-amino acids to d-isomers and concurrent formation of cross-linked amino acids such as lysinoalanine. Racemization of l-amino acids residues to their d-isomers in food and other proteins is pH-, time-, and temperature-dependent. Although racemization rates of the 18 different l-amino acid residues in a protein vary, the relative rates in different proteins are similar. The diet contains both processing-induced and naturally formed d-amino acids. The latter include those found in microorganisms, plants, and marine invertebrates. Racemization impairs digestibility and nutritional quality. The nutritional utilization of different d-amino acids varies widely in animals and humans. In addition, some d-amino acids may be both beneficial and deleterious. Thus, although d-phenylalanine in an all-amino-acid diet is utilized as a nutritional source of l-phenylalanine, high concentrations of d-tyrosin...

Chemistry, nutrition, and microbiology of D-amino acids.

The d-enantiomers of amino acids have been thought to have relatively minor functions in biological processes. While l-amino acids clearly predominate in nature, d-amino acids are sometimes found in proteins that are not synthesized by ribosomes, and d-Ala and d-Glu are routinely found in the peptidoglycan cell wall of bacteria. Here, we review recent findings showing that d-amino acids have previously unappreciated regulatory roles in the bacterial kingdom. Many diverse bacterial phyla synthesize and release d-amino acids, including d-Met and d-Leu, which were not previously known to be made. These noncanonical d-amino acids regulate cell wall remodeling in stationary phase and cause biofilm dispersal in aging bacterial communities. Elucidating the mechanisms by which d-amino acids govern cell wall remodeling and biofilm disassembly will undoubtedly reveal new paradigms for understanding how extracytoplasmic processes are regulated as well as lead to development of novel therapeutics.

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Emerging knowledge of regulatory roles of d-amino acids in bacteria

Fulicin, a novel neuropeptide containing a D-amino acid residue isolated from the ganglia of Achatina fulica.

Structure and action of Molluscan neuropeptides

A number of neuropeptides were isolated from the ganglia and muscles of molluscs, and their actions were examined. Diverse neuropeptides, in addition to several classical neurotransmitters, were suggested to be involved in the regulation of the anterior byssus retractor muscle ofMytilus. A wide structural variety of members of theMytilus inhibitory peptide family was observed in each of the generaMytilus, Achatina andHelix. Gly-Trp-NH2, the C-terminal dipeptide fragment of the neuropeptide AGPWamide, showed a more potent action than the parent peptide in all of the muscles examined. Peptides related to some molluscan neuropeptides were found to be distributed interphyletically. Some neuropeptides containing ad-amino acid residue were found inAchatina andMytilus. These aspects of molluscan neuropeptides are thought not to be exceptional.

Makoto Kobayashi

Papers

Fulicin, a novel neuropeptide containing a D-amino acid residue isolated from the ganglia of Achatina fulica.

Structure and action of Molluscan neuropeptides

Comparative aspects of structure and action of molluscan neuropeptides.

Purification of achatin-I from the atria of the African giant snail, Achatina fulica, and its possible function.

A novel cardio-excitatory peptide isolated from the atria of the African giant snail, Achatina fulica.