L-Xylulose is an endogenous metabolite present in Blood, Cerebrospinal_Fluid and Urine that can be used for the research of Ribose 5 Phosphate Isomerase Deficiency.
Endogenous metabolites is defined as those that are annotated by Kyoto Encyclopedia of Genes and Genomes as substrates or products of the ~1900 metabolic enzymes encoded in our genome. It is clear in the body of literature that there are documented toxic properties for many of these metabolites[1].
References:
[1]. Lee N, et al. Endogenous toxic metabolites and implications in cancer therapy. Oncogene. 2020 Aug;39(35):5709-5720.
[2]. Huck JH, et al. Ribose-5-phosphate isomerase deficiency: new inborn error in the pentose phosphate pathway associated with a slowly progressive leukoencephalopathy. Am J Hum Genet. 2004 Apr;74(4):745-51.