Discovery of PPi-type Phosphoenolpyruvate Carboxykinase Genes in Eukaryotes and Bacteria.
Phosphoenolpyruvate carboxykinase (PEPCK) is one of the pivotal enzymes that regulates the carbon flow of the central metabolism by fixing CO2 to phosphoenolpyruvate (PEP) to produce oxaloacetate or vice versa. Whereas ATP- and GTP-type PEPCKs have been well studied, and their protein identities are established, inorganic pyrophosphate (PPi)-type PEPCK (PPi-PEPCK) is poorly characterized. Despite extensive enzymological studies, its protein identity and encoding gene remain unknown. In this study, PPi-PEPCK has been identified for the first time from a eukaryotic human parasite, Entamoeba histolytica, by conventional purification and mass spectrometric identification of the native enzyme, followed by demonstration of its enzymatic activity. A homolog of the amebic PPi-PEPCK from an anaerobic bacterium Propionibacterium freudenreichii subsp. shermanii also exhibited PPi-PEPCK activity. The primary structure of PPi-PEPCK has no similarity to the functional homologs ATP/GTP-PEPCKs and PEP carboxylase, strongly suggesting that PPi-PEPCK arose independently from the other functional homologues and very likely has unique catalytic sites. PPi-PEPCK homologs were found in a variety of bacteria and some eukaryotes but not in archaea. The molecular identification of this long forgotten enzyme shows us the diversity and functional redundancy of enzymes involved in the central metabolism and can help us to understand the central metabolism more deeply.
From the Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan, the Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan, and.
Yoko
Y
Chiba
the Graduate School of Environmental Studies, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu cho, Kyoto, Kyoto 606-8501, Japan.
Ryoma
R
Kamikawa
the Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan, and.
Kumiko
K
Nakada-Tsukui
the Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan, and.
Yumiko
Y
Saito-Nakano
From the Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan, the Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan, and nozaki@nih.go.jp.
Tomoyoshi
T
Nozaki
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004748:Entamoeba histolytica / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics* / Q000378:metabolism; D011424:Propionibacterium / Q000201:enzymology / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D015800:Protozoan Proteins; D019764:Phosphoenolpyruvate Carboxykinase (ATP)
carbohydrate metabolism; carbon fixation; central metabolism; enzyme; novel enzyme; parasite metabolism; phosphoenolpyruvate carboxykinase; pyrophosphate