TBIO-14. CHARACTERISATION OF THE ARGININE PATHWAY ENZYMES IN PAEDIATRIC BRAIN TUMOURS TO DETERMINE SUSCEPTIBILITY TO THERAPEUTIC ARGININE DEPLETION

INTRODUCTION Extracellular arginine dependency (auxotrophy) is increasingly being recognised in several tumours. This is due to the inability of cancer cells to recycle or synthesise intracellular arginine through the urea cycle pathway compared to normal cells. Whilst adult glioblastoma is known to exhibit this, the expression of the arginine pathway enzymes has not been delineated in paediatric brain tumours. METHODS We used immunohistochemical methods to stain for arginine pathway enzymes in Paediatric High grade glioma (pHGG), low grade glioma (pLGG) and medulloblastoma (MB) tumour tissue microarrays (TMAs). The antibodies detected protein expression of the metaboliser Arginase (Arg2), recycling enzymes ornithine transcarbamoylase (OTC), Arginosuccinate synthetase (ASS1) and arginosuccinate lyase (ASL) as well as the transporter SLC7A1. RESULTS Deficiency of OTC, ASS1 and ASL were seen in 92%, 98% and 93% of pHGG samples (n=156) respectively, with deficiency defined as low (<20%) or negative antibody expression. Identical results were seen in pLGG (n=98) - 83%, 97% and 95% were deficient in OTC, ASS1 and ASL. Both pHGG and pLGG highly expressed SLC7A1 and Arg2, demonstrating that they could transport and utilise arginine. In MB (n=82), this auxotrophic signature was again seen in 90% of TMAs with absent or low expression of OTC, ASS1 and ASL and high Arg2 and SLC7A1 expression. CONCLUSIONS These results show that pHGG, pLGG and MB are arginine auxotrophs. Pegylated arginase (BCT-100) is currently in Phase I/II trials in relapsed pHGG. Our results suggest that therapeutic arginine depletion may also be useful in MB and pLGG.

Cloning and Purification of Ornithine Transcarbamoylase from Lactobacillus brevis and Its Application on Regulating Ethyl Carbamate Formation in Chinese rice wine

It was studied that ornithine transcarbamoylase played important roles in ethyl carbamate (EC) formation. Ornithine transcarbamoylase (OTCase) can degrade citrulline, a precursor of EC, through arginine deiminase pathway. Therefore, they are generally added to regulate EC catabolism in rice wine fermentation. In this work, OTCase were added in different concentration and ferment time. It turned out addition of OTCase could reduce EC to some extent, especially for low concentration enzyme addition and mid-stage addition time. Furthermore, the production of amino acids, volatile flavor compounds and sense of taste were not markedly affected. The discoveries reveal that EC can be reduced by supplying OTCase while rice wine leavening. Key words: Ethyl carbamate, Ornithine transcarbamoylase, Rice wine fermentation, Enzyme inhibition

Expression ofSTM4467-Encoded Arginine Deiminase Controlled by theSTM4463Regulator Contributes to Salmonella enterica Serovar Typhimurium Virulence

ABSTRACTArginine deiminase (ADI), carbamate kinase (CK), and ornithine transcarbamoylase (OTC) constitute the ADI system. In addition to metabolic functions, the ADI system has been implicated in the virulence of certain pathogens. The pathogenic intracellular bacteriumSalmonella entericaserovar Typhimurium possesses theSTM4467,STM4466, andSTM4465genes, which are predicted to encode ADI, CK, and OTC, respectively. Here we report that theSTM4467gene encodes an ADI and that ADI activity plays a role in the successful infection of a mammalian host byS. Typhimurium. AnSTM4467deletion mutant was defective for replication inside murine macrophages and was attenuated for virulence in mice. We determined that a regulatory protein encoded by theSTM4463gene functions as an activator forSTM4467expression. The expression of the ADI pathway genes was enhanced inside macrophages in a process that required STM4463. Lack of STM4463 impaired the ability ofS. Typhimurium to replicate within macrophages. A mutant defective inSTM4467-encoded ADI displayed normal production of nitric oxide by macrophages.