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D-amino acids are used as components of pharmaceutical products, such as antibiotics, anticoagulants, and pesticides, because they have been shown to be not only more potent than their L enantiomers, but also more resistant to enzyme degradation.

D-amino acid dehydrogenase enzymes have been synthesized via mutagenesis with an ability to produce straight, branched, cyclic aliphatic and aromatic D-amino acids.

Solubilized D-amino acid dehydrogenase tends to increase its affinity for D-alanine, D-asparagine, and D-$$\alpha$$-amino-n-butyrate.

In E. coli K12 D-amino acid dehydrogenase is most active with D-alanine as its substrate, as this amino acid is the sole source of carbon, nitrogen, and energy. The enzyme works optimally at pH 8.9 and has a Michaelis constant for D-alanine equal to 30 mM. DAD discovered in gram-negative E. coli B membrane can convert L-amino acids into D-amino acids as well.

Volkensin - eukaryotic protein synthesis inhibitor

Properties: a glycoprotein, has an A subunit and a B subunit linked by disulfide bridges and non-covalent bonds, galactose specific lectin, can inhibit protein synthesis in whole cells and in cell-free systems, such as lysates. can be included amongst ricin like toxins, and resembles modeccin, the toxin of Adenia digitata. Although mostly similar in composition, volkensin and modeccin differ in that volkensin contains more half cysteine residues and more than twice as much sugar, due to high content of galactose and mannose. In addition, volkensin is able to inhibit protein synthesis at concentrations 10 times lower than required for modeccin.

B subunit is responsible for binding to the galactosyl-terminated receptors on the cell membrane that allows the entry the A subunit of the toxin into the cell, which performs the inhibitory function.

Volkensin, and toxins alike are studied to understand protein entry into the cell and many have been found to have antitumor applicability. Have been also found to agglutinate red blood cells without any specificity for a particular blood group.

The toxin can be isolated via affinity chromatography, using acid-treated Sepharose 6B.

Rats poisoned with higher doses died between 7 and 12 h after administration. They appeared normal for 1-2 h after poisoning and then they became progressively sedated until death, which occurred suddenly, preceded by shortlasting seizures. The rats which received lower doses and died after several days often showed ascites and wax-like peritoneal fat, a sign of pancreatic lesion.

From gene sequencing analysis, volkensin was found to be coded by 1569-bp ORF, that is 523 amino acid residues without introns. The internal linker sequence is 45 bp. The active site of the A subunit contains Ser203, a novel residue that is conserved in all ribosome inactivating proteins.

Experiments performed in vitro showed increased toxicity of volkensin to microglia and astrocytes.