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SIRT4 is a mitochondrial ADP-ribosyltransferase that inhibits mitochondrial glutamate dehydrogenase 1 activity, thereby downregulating insulin secretion in response to amino acids. [7] A deacetylation of malonyl-CoA decarboxylase enzyme by SIRT4 represses the enzyme activity, inhibiting fatty acid oxidation in muscle and liver cells.
SIRT3, a mitochondrial protein deacetylase, plays a role in the regulation of multiple metabolic proteins like isocitrate dehydrogenase of the TCA cycle. It also plays a role in skeletal muscle as a metabolic adaptive response. Since glutamine is a source of a-ketoglutarate used to replenish the TCA cycle, SIRT4 is involved in glutamine metabolism.
RNA and DNA contain only right-handed sugars; proteins are exclusively composed of left-handed amino acids, although many bacteria and fungi are able to synthesise non-ribosomal peptides containing right-handed amino acids, as the example of peptidoglycan synthesis shows. This phenomenon is known as homochirality. [11]
A conservative replacement (also called a conservative mutation or a conservative substitution or a homologous replacement) is an amino acid replacement in a protein that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size). [1] [2]
S-Aminoethyl-l-cysteine, also known as thialysine, is a toxic analog of the amino acid lysine in which the second carbon of the amino acid's R-group (side chain) has been replaced with a sulfur atom. Strictly speaking, L-thialysine is actually considered an S-(2-aminoethyl) analogue of L-cysteine.
Like other natural proteinogenic amino acids, cysteine and selenocysteine have L chirality in the older D / L notation based on homology to D - and L-glyceraldehyde. In the newer R / S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, they have R chirality, because of the presence of sulfur or ...
Cycloheximide is a naturally occurring fungicide produced by the bacterium Streptomyces griseus.Cycloheximide exerts its effects by interfering with the translocation step in protein synthesis (movement of two tRNA molecules and mRNA in relation to the ribosome), thus blocking eukaryotic translational elongation.
Seven of 12 amino acids surrounding tryptophan are the same in C- and N-domain, the biggest difference is that 2 bulky and hydrophobic amino acids in the C-domain have been replaced with 2 smaller and polar amino acids in the N-domain.