Publications

• Removal of phosphoglycolate in hyperthermophilic archaea.

  Michimori Y., Izaki R., Su Y., Fukuyama Y., Shimamura S., Nishimura K., Miwa Y., Hamakita S., Shimosaka T., Makino Y., Takeno R., Sato T., Beppu H., Cann I., Kanai T., Nunoura T., Atomi H.

  Many organisms that utilize the Calvin-Benson-Bassham (CBB) cycle for autotrophic growth harbor metabolic pathways to remove and/or salvage 2-phosphoglycolate, the product of the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). It has been presumed that the occurren ... >> More

  Many organisms that utilize the Calvin-Benson-Bassham (CBB) cycle for autotrophic growth harbor metabolic pathways to remove and/or salvage 2-phosphoglycolate, the product of the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). It has been presumed that the occurrence of 2-phosphoglycolate salvage is linked to the CBB cycle, and in particular, the C2 pathway to the CBB cycle and oxygenic photosynthesis. Here, we examined 2-phosphoglycolate salvage in the hyperthermophilic archaeon <i>Thermococcus kodakarensis</i>, an obligate anaerobe that harbors a Rubisco that functions in the pentose bisphosphate pathway. <i>T. kodakarensis</i> harbors enzymes that have the potential to convert 2-phosphoglycolate to glycine and serine, and their genes were identified by biochemical and/or genetic analyses. 2-phosphoglycolate phosphatase activity increased 1.6-fold when cells were grown under microaerobic conditions compared to anaerobic conditions. Among two candidates, TK1734 encoded a phosphatase specific for 2-phosphoglycolate, and the enzyme was responsible for 80% of the 2-phosphoglycolate phosphatase activity in <i>T. kodakarensis</i> cells. The TK1734 disruption strain displayed growth impairment under microaerobic conditions, which was relieved upon addition of sodium sulfide. In addition, glycolate was detected in the medium when <i>T. kodakarensis</i> was grown under microaerobic conditions. The results suggest that <i>T. kodakarensis</i> removes 2-phosphoglycolate via a phosphatase reaction followed by secretion of glycolate to the medium. As the Rubisco in <i>T. kodakarensis</i> functions in the pentose bisphosphate pathway and not in the CBB cycle, mechanisms to remove 2-phosphoglycolate in this archaeon emerged independent of the CBB cycle. << Less

  Proc Natl Acad Sci U S A 121:e2311390121-e2311390121(2024) [PubMed] [EuropePMC]

  This publication is cited by 21 other entries.

• Murine alanine aminotransferase: cDNA cloning, functional expression, and differential gene regulation in mouse fatty liver.

  Jadhao S.B., Yang R.-Z., Lin Q., Hu H., Anania F.A., Shuldiner A.R., Gong D.-W.

  Alanine aminotransferase (ALT) is a widely used index of liver integrity or hepatocellular damage in clinics as well as a key enzyme in intermediatary metabolism. In this study, we have cloned the complementary DNAs of murine homologues of human alanine aminotransferase 1 and 2 (ALT1 and ALT2). Th ... >> More

  Alanine aminotransferase (ALT) is a widely used index of liver integrity or hepatocellular damage in clinics as well as a key enzyme in intermediatary metabolism. In this study, we have cloned the complementary DNAs of murine homologues of human alanine aminotransferase 1 and 2 (ALT1 and ALT2). The deduced peptides of murine ALT1 (mALT1) and ALT2 (mALT2) share 87% and 93% identity, respectively, with their human counterparts at the amino acid level. Murine ALT genes localize to separate chromosomes, with mALT1 gene (gpt1) on chromosome 15 and mALT2 gene (gpt2) on chromosome 8. The murine gpt1 and gpt2 differ in messenger RNA expression: gpt1 is mainly expressed in liver, bowel, and white adipose tissue and gpt2 is highly expressed in muscle, liver, and white adipose tissue. Expression of recombinant mALT1 and mALT2 proteins in Escherichia coli (E. coli) produced functional enzymes that catalyze alanine transamination. The potential diagnostic value of ALT isoenzymes in liver disease was evaluated in an obese animal model. In fatty livers of obese mice, ALT2 gene expression is induced 2-fold, but ALT1 remains the same. Furthermore, in fatty liver, total hepatic ALT activity is elevated significantly by 30% whereas aspartate aminotransferase (AST) activity remains unchanged. In conclusion, these results indicate that ALT2 may be responsible for the increased ALT activity in hepatic steatosis and provide evidence that an ALT isoenzyme-specific assay may have more diagnostic value than the total ALT activity assay currently in clinical use. << Less

  Hepatology 39:1297-1302(2004) [PubMed] [EuropePMC]

• cDNA cloning, genomic structure, chromosomal mapping, and functional expression of a novel human alanine aminotransferase.

  Yang R.-Z., Blaileanu G., Hansen B.C., Shuldiner A.R., Gong D.-W.

  Alanine aminotransferase (ALT) catalyzes the reversible transamination between alanine and 2-oxoglutarate to form pyruvate and glutamate, and thereby has a key role in the intermediary metabolism of glucose and amino acids. Two ALT isoenzymes are known to exist, but only one ALT gene has been clon ... >> More

  Alanine aminotransferase (ALT) catalyzes the reversible transamination between alanine and 2-oxoglutarate to form pyruvate and glutamate, and thereby has a key role in the intermediary metabolism of glucose and amino acids. Two ALT isoenzymes are known to exist, but only one ALT gene has been cloned, GPT. In this study, we cloned a homolog of GPT and named it GPT2, and the corresponding protein ALT2. GPT2 shares 69% identity and 78% similarity at the protein level to the previously cloned GPT. The human gene GPT2 encodes a 3.9-kb mRNA, consists of 12 exons, spanning approximately 50 kb of the genome, and maps to chromosome 16q12.1. GPT2 and GPT differ in mRNA expression in that GPT2 is highly expressed in muscle, fat, and kidney, whereas GPT is mainly expressed in kidney, liver, and heart. In addition, GPT2 seems to be the predominant form of GPT at the mRNA level in these tissues. Expression of ALT2 protein in Escherichia coli produced a functional recombinant enzyme that catalyzes alanine transamination, confirming that the enzyme is an ALT. The more abundant expression of GPT2 than GPT, especially in muscle and fat, suggests a unique and previously unrecognized role of this gene product in glucose, amino acid, and fatty acid metabolism and homeostasis. << Less

  Genomics 79:445-450(2002) [PubMed] [EuropePMC]