Molecular evolution of biotin‐dependent carboxylases

Abstract

Amino-acid sequences of three functional units from various biotin-dependent carboxylases, biotin carboxylase, biotin-carboxyl-carrier protein and carboxyl transferase, were investigated by computer-assisted sequence comparison to obtain information about the structure, function, and molecular evolution of the enzymes. Biotin-dependent carboxylases, except transcarboxylase and oxaloacetate decarboxylase which lack biotin carboxylase, exert their catalytic activities through the three functional units. The three functional units correspond with functional domains or subunits of the enzymes, and the genetic information for the units is encoded in different ways from enzyme to enzyme. It is known that biotin carboxylase is homologous to carbamoyl-phosphate synthetase, and that the biotin-carboxyl-carrier protein is homologous to lipoic-acid-binding domain. The evolutionary relationships between the functional units and their homologues were described. A model for the evolutionary history of the enzymes was proposed by molecular phylogenetic analysis, which shows how a wide variety of domain andor subunit structures for the enzymes may have been established. A repeated structure was found in biotin-carboxyl-carrier protein, and the secondary structure of the protein was predicted using the observed sequence similarity with a lipoic-acidbinding domain.The biotin-dependent carboxylases constitute a diverse group of enzymes, which includes acetyl-CoA carboxylase, propionyl-CoA carboxylase, oxaloacetate decarboxylase, pyruvate carboxylase and transcarboxylase. The enzymes are involved in a variety of essential metabolic pathways such as lipogenesis, gluconeogenesis and amino-acid metabolism. In addition, these enzymes have been identified in animals,

Biochemical and Molecular Biological Characterization of CAC2, the Arabidopsis thaliana Gene Coding for the Biotin Carboxylase Subunit of the Plastidic Acetyl-Coenzyme A Carboxylase

“…tifiable via sequence comparisons, the ATP-binding site, and a domain that is similar to carbamoyl-phosphate synthetase (Toh et al, 1993). This latter domain is probably involved in the synthesis of the product of biotin carboxylase, carboxy-biotin, a reaction mechanistically related to the synthesis of carbamoyl phosphate.…”

“…The sequence similarities between CAC2 and the homologs shown in Figure 1 were particularly high in four domains. These include the ATP-binding domain and a domain that showed sequence similarity to carbamoylphosphate synthetase (Toh et al, 1993).…”

HFA1 Encoding an Organelle-specific Acetyl-CoA Carboxylase Controls Mitochondrial Fatty Acid Synthesis in Saccharomyces cerevisiae

“…biotin carboxylase, biotincarboxyl-carrier protein, and transcarboxylase (8). Depending on the organism, these components represent either three distinct proteins or they are contained as functional domains within difunctional or trifunctional ACC proteins (9). In yeast, cytoplasmic ACC is a single trifunctional polypeptide of 2233 amino acids and with an approximate molecular mass of 250 kDa (10 -12).…”

A Maize Acetyl-Coenzyme A Carboxylase cDNA Sequence

“…The predicted polypeptide of 2325 amino acids contains a biotinylation site at position 806, within the conserved M K M motif (Toh et al, 1993). Functional domains of the maize ACCase polypeptide are in the order biotin carboxylase, biotin carboxyl carrier protein, carboxyltransferase.…”