Propionylated lysine

The way biotin participates in carbon dioxide fixation was established in the early 1960s. In 1961 Kaziro and Ochoa using propionyl CoA carboxylase provided evidence for 14C02 binding in an enzyme-biotin complex. With excess propionyl CoA the 14C label moved into a stable position in methyl malonyl CoA. In the same year Lynen found biotin itself could act as a C02 acceptor in a fixation reaction catalyzed by B-methylcrotonyl CoA carboxylase. The labile C02 adduct was stabilized by esterification with diazomethane and the dimethyl ester shown to be identical with the chemically synthesized molecule. X-ray analysis of the bis-p-bromanilide confirmed the carbon dioxide had been incorporated into the N opposite to the point of attachment of the side chain. Proteolytic digestion and the isolation of biocytin established the biotin was bound to the e-NH2 of lysine. 

A closely related disease is caused by a deficiency of propionyl-CoA carboxylase.3 This may be a result of a defective structural gene for one of the two subunits of the enzyme, of a defect in the enzyme that attaches biotin to carboxylases, or of biotinitase, the enzyme that hydrolytically releases biotin from linkage with lysine (Chapter 14). The latter two defects lead to a multiple carboxylase deficiency and to methylmalonyl aciduria as well as ketoacidosis and propionic acidemia. ... 

Numerous undesirable reactions that result in organoleptic, nutritional and functional deterioration may occur in food proteins during processing and storage. These include the non-enzymatic or Maillard reactions, transamidation condensation reactions with dehydroalanine forming crosslinks, and carbonyl amine interactions, all of which may involve the free e-amino group of lysine (11,23). To minimize these reactions a significant volume of work has been done on the protective modification of the e-NH2 of lysine by formylation, acetylation, propionylation (26) or reductive dimethylation (10,11). 

The synthesis of malonyl CoA is catalyzed by acetyl CoA carboxylase, which contains a biotin prosthetic group. The carboxyl group of biotin is covalently attached to the e amino group of a lysine residue, as in pyruvate carboxylase (Section 16.3.2) and propionyl CoA carboxylase (Section 22.3.3). As with these other enzymes, a carboxybiotin intermediate is formed at the expense of the hydrolysis a molecule of ATP. The activated CO2 group in this intermediate is then transferred to acetyl CoA to form malonyl CoA. 

The important function of biotin is its role as coenzyme for carboxylase, which catalyses carbon dioxide fixation or carboxylation reaction. The epsilon amino group of lysine in carboxylase enzymes combines with the carboxyl group of biotin to form covalently linked biotinyl carboxyl carrier protein (BCCP or biocytin) (Figure 6.8). This serves as an intermediate carrier of carbon dioxide. The carboxylation of acetyl CoA to malonyl CoA in presence of acetyl CoA carboxylase requires biotin as coenzyme. Propionyl carboxylase and pyruvate carboxylase are also associated with biotin. 

The coenzyme form of pantothenic acid is coenzyme A and is represented as CoASH. The thiol group acts as a carrier of acyl group. It is an important coenzyme involved in fatty acid oxidation, pyruvate oxidation and is also biosynthesis of terpenes. The epsilon amino group of lysine in carboxylase enzymes combines with the carboxyl carrier protein (BCCP or biocytin) and serve as an intermediate carrier of C02. Acetyl CoA pyruvate and propionyl carboxylayse require the participation of BCCP. The coenzyme form of folic acid is tetrahydro folic acid. It is associated with one carbon metabolism. The oxidised and reduced forms of lipoic acid function as coenzyme in pyruvate and a-ketoglutarate dehydrogenase complexes. The 5-deoxy adenosyl and methyl cobalamins function as coenzyme forms of vitamin B12. Methyl cobalamin is involved in the conversion of homocysteine to methionine. 

Biotin is a water-soluble vitamin. It is a cofactor for four ATP-dependent carboxylases acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, and p-methylcrotonyl-CoA carboxylase. Biotin occurs covalently bound to the enzymes via the terminal amino group of a lysine residue. With the normal and continual turnover of these enzymes in the body, the biotin is released, but then utilized again as a cofactor when the enzymes are re-synthesized. The structure of biotin is shown in Figure 9.32,... 

The leupeptins are Inhibitors of plasmin, a trypsin-like enzyme. Leupeptlns contain arginlnyl residues at their terminal carbon, and inhibit enzymes which cleave at the carboxyl side of basic amino acids such as arginine or lysine.50 The structure of the most active leupeptin mixture is propionyl-L-Leu-L-Leu-Argininal and acetyl-L-Leu-L-Leu-Arglnlnal in a 3 1 ratio.64-66... 

Bjamason and Carpenter (38, 52, 53) studied the use of formylation, acetylation, and propionylation for blocking amino groups in food proteins. Many of these chemical modifications could be easily applied on a commercial scale. The formyl and acetyl derivatives were nutritionally utilized at least partially. The propionylated lysine was not utilized however the propionylated lactalbumin was partially utilized (Table VII). The acylation procedure lowered considerably the extent of the Maillard reaction. Previous investigations, in support of the observations of Bjamason and Carpenter, have shown deacylase in the kidney (51). 

Treatment of the biocytin derivative with biotini-dase, an enzyme that splits the bond between biotin and lysine, yields l -N-methoxy-Ci4-carbonylbiotin. This mode of attachment of CO2 to biotin (in the L-N position) and of biotin to the apoenzyme (6-N-(+) biotinyl lysyl) proved to be identical for j8-methyl-crotonyl CoA carboxylase, propionyl CoA carboxyyl-ase, and oxaloacetic transcarboxylase. The binding of CO2 with biotin is a high-energy binding ( — 4.7 kilocalories per mole) and the CO2 bond to the L-N-meth-oxy-Ci4-carbonylbiotin can be considered as a form of activated CO2. 

In one synthetic approach (Veld 1990, 1992), alanine is first converted to the bromo derivative via the reaction of the diazonium salt of the amine with hydrogen bromide. In the next step the acid functionality is activated by converting it to the acid chloride using thionyl chloride. The activated acid is condensed with a protected a-amino acid to yield the dipeptide intermediate which is then cyclized by heating in presence of Celite (ion exchange resin) to yield the final product. However, the overall yield of this reaction is fairly low. A more elegant approach is shown in Scheme 5. In this approach, an a-amino acid wth a protected side chain (e.g., e-Z-lysine) is reacted with 2-bromo-propionyl bromide under Schotten-Bauman condidons (Fischer 1908) to yield the intermediate 5a, which is then cyclized under basic conditions to the depsipeptide 5b. 

Biotin serves as a covalently bound coenzyme for acetyl-CoA carboxylases (ACC) 1 and 2, pyruvate carboxylase (PC), propionyl-CoA carboxylase (PCQ and 3-methylcrotonyl-CoA carboxylase (MCQ in mammals and other metazoans (Zempleni et al. 2009). Additional carboxylases exist in microbes (Knowles 1989). The attachment of biotin to the s-amino group of a spedlic lysine residue in holocarboxylases is catalysed by holocarboxylase synthetase (HLCS) or microbial orthologs such as BirA. Biotinylation of carboxylases requires ATP to produce the energy-rich intermediate biotinyl-5 -AMP (Zempleni et al. 2009). 

Biotinidase deficiency [1, 2] is a form of multiple carboxylase deficiency in which the failure to cleave biocytin to yield biotin and lysine leads to biotin deficiency, producing deficient activity of each of the carboxylases, especially the mitochondrial enzymes propionyl-CoA carboxylase, 3-methylcrotonyl CoA carboxylase and pyruvate carboxylase. 

Biotin is the prosthetic group of carboxylating enzymes, such as acetyl-CoA-carboxylase, pyruvate carboxylase and propionyl-CoA-carboxylase, and therefore plays an important role in fatty acid biosynthesis and in gluconeo-genesis. The carboxyl group of biotin forms an amide bond with the e-amino group of a lysine residue of the particular enzyme protein. Only the (3aS, 4S, 6aR) compound, D-(-i-)-biotin, is biologically active ... 

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