@chemedits: inspiration @perhaps_worthy review by Das, Balaram, & Sanyal, 2024, Amino Acid Chirality: Stereospecific Conversion and Physiological Implications "Molecular asymmetry, a vital feature of all living systems, dictates the architecture and functioning of almost all biomolecules. Historically grown out of one of the most central discoveries of Louis Pasteur on tartaric acid, (2) it is now well accepted that chirality arising from the spatial arrangement of four different atoms or groups bonded to a central carbon atom is integral to all biomolecules. Emil Fischer arbitrarily fixed the absolute configuration of the isomer pair of glyceraldehyde as l and d and related this to the absolute configuration of various other chiral molecules, including amino acids. (3) The pentose sugar moiety is in the d-form in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). In contrast, amino acids in proteins synthesized in ribosomes are in the l-configuration except for the achiral glycine. (4) Nineteen l-amino acids (LAA), together with achiral glycine, are universally accepted by the cellular translation machinery as building blocks for protein synthesis (two additional amino acids, l-selenocysteine and l-pyrrolysine, are used by some organisms, but are not universal). (5) LAAs participate in myriad biological processes acting as signaling molecules for cell proliferation, second messengers in intracellular communication, intermediate metabolites in biochemical pathways, or playing critical roles in pathogenic responses in mammals and plants. (6) For each LAA, there exists a nonsuperimposable chiral counterpart in d-configuration called an enantiomer (Figure 1A). Several d-amino acids (DAAs), although similar to their LAA counterparts in terms of physical and chemical properties, have been implicated in unique and diverse physiological roles in microbes, plants, invertebrates, and higher organisms, roles not met by their l-counterparts." #biochem #apbio #ochem #organicchemistry

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Sunday 17 August 2025 15:32:26 GMT