Diversity of dioxygenases that catalyze the first step of oxidation of long-chain n-alkanes in Acinetobacter sp. M-1

Abstract Three kinds of enzymes, designated A, B and C, involved in n -alkane oxidation were found in the cytoplasm of n -alkanegrown Acinetobacter sp. M-1. All catalyzed the dioxygenation of n -alkanes to the corresponding n -alkyl hydroperoxides. Purified enzyme A consisted of four identical subunits having a molecular mass of 72 kDa. The enzyme was strongly inhibited by several iron-chelating agents, such as o -phenanthroline, 8-hydroxyquinoline and α,α'-dipyridyl, and could be distinguished from enzyme C, a Cu²⁺-requiring flavoprotein. Enzyme B was relatively unstable on purification. The three enzymes used n -alkanes, n -alkenes, and aryl compounds with longer alkyl side chains as substrates. Enzymes B and C were more active toward relatively short n -alkanes (C_12–16). Enzyme A oxidized solid n -alkanes well, the most preferable substrate being tetracosane (C₂₄). Enzyme A is responsible for about 80% of the total activity found in the soluble fraction of n -alkane-grown Acinetobacter sp. M-1, indicating that the enzyme plays a major role during growth on solid n -alkanes.     

5′-CMP and 5′-UMP promote myogenic differentiation and mitochondrial biogenesis by activating myogenin and PGC-1α in a mouse myoblast C2C12 cell line

Ribonucleotides are basic monomeric building blocks for RNA considered as conditionally essential nutrients. They are normally produced in sufficient quantity, but can become insufficient upon stressful challenges. The administration of pyrimidine nucleotides, such as cytidine-5′-monophosphate (5′-CMP) and uridine-5′-monophosphate (5′-UMP), enables rats to endure prolonged exercise. However, the underlying mechanisms have remained elusive. To investigate these mechanisms, we studied the effect of 5′-CMP and 5′-UMP on muscular differentiation and mitochondrial biogenesis in myoblast C2C12 cells. 5′-CMP and 5′-UMP were found to increase the mRNA levels of myogenin, which is a myogenic regulatory protein expressed during the final differentiation step and fusion of myoblasts into myotubes. 5′-CMP and 5′-UMP also promoted myoblast differentiation into myotube cells. 5′-CMP and 5′-UMP further increased the mRNA levels of PGC-1α which regulates mitochondrial biogenesis and skeletal muscle fiber type. In addition, 5′-CMP and 5′-UMP increased mitochondrial DNA copy number and enhanced mRNA levels of slow-muscle myosin heavy chains. Moreover, cytidine and uridine, nucleosides corresponding to 5′-CMP and 5′-UMP, markedly promoted myotube formation in C2C12 cells. Considering the metabolism and absorption of nucleotides, the active bodies underlying the effects observed with 5′-CMP and 5′-UMP could be cytidine and uridine. In conclusion, our results indicate that 5′-CMP and 5′-UMP can promote myogenic differentiation and mitochondrial biogenesis, as well as increase slow-twitch fiber via the activation of myogenin and PGC-1α. In addition, 5′-CMP and 5′-UMP may be considered as safe and effective agents to enhance muscle growth and improve the endurance in skeletal muscles.