Biochemical Pathways

The study of biochemical pathways is critical in metabolic research to evaluate quantitative reactions, cellular/molecular processes, and functional rates of flux. Pathways encompass various types of biosynthesis (e.g., for secondary metabolites), biodegradation (e.g., xenobiotics), and metabolism (e.g., of amino acids, carbohydrates, nucleotides, vitamins). CIL offers stable isotope-labeled compounds that span metabolic pathways present in different organisms.

Listed here are examples of human biochemical pathways (e.g., glycolysis, pentose phosphate, TCA or Krebs, urea). Please inquire if an alternate compound, label, or quantity is desired. 

Related Resources

➤ Stable Isotope Standards for Mass Spectrometry
➤ TCA Cycle Mixtures

Stable Isotope-Labeled Products for Metabolic Research

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Product category

Folate Cycle

Glycolysis

Glutamate/Glutamine Cycle

Methionine Cycle

Pentose Phosphate Pathway

TCA Cycle

Tryptophan Pathway

Urea Cycle

Isotope Label

Label Type

Isotopic Enrichment Range

Grade

Molecular Weight Range

Product Form

Product Form 2

Folate Cycle

The folate metabolic pathway plays a central role in many physiological processes (e.g., redox and amino acid homeostasis) and biochemical reactions. The reactions include, but are not limited to, the synthesis of nucleotides and amino acids (e.g., methionine, homocysteine) and mitochondrial protein translation. Inhibited or abnormal functions have been linked to systemic diseases (e.g., cardiovascular, neurodegenerative). To assist in compound identification/quantification and their functional assessment, CIL offers a collection of folate cycle-related metabolites. Included in the offering is the metabolite 5-methyl-tetrahydrofolate (5-methyl-THF), which is linked to the methionine cycle, as well as other metabolic intermediates and reactants. These are available as research grade materials in predominantly their neat form.

Glutamate/Glutamine Cycle

The glutamate-glutamine cycle plays an important role in the maintenance of cellular function. Although these amino acids are considered nonessential in mammals, both are vital precursors to various syntheses (e.g., amino acids – aspartate, γ-aminobutyric acid or GABA; peptides – oxidized/reduced glutathione) and help with energy homeostasis. Included in this metabolic pathway is the synthesis of α-ketoglutarate (a key intermediate of the TCA cycle) and is therefore indirectly involved in energy production as well. Dysfunction or abnormality in the glutamate-glutamine cycle has been correlated to mental health disorders (e.g., schizophrenia) and neurodegenerative diseases (e.g., Alzheimer’s). To aid biomarker and metabolism studies in this research space, CIL is pleased to offer its related metabolites in their stable isotope-labeled and/or unlabeled form as neat materials.

Glycolysis

Glycolysis is the metabolic pathway that converts glycose to pyruvate in a 10-step reaction, while using the energy released toward cellular metabolism. This catabolic pathway is universal, occurring in both prokaryotic and eukaryotic cells. To complement the analysis of metabolites in this pathway, CIL is pleased to offer a number of its stable isotope-labeled compounds. The compound offering encompasses the pathway end points (i.e., glucose and pyruvate) and its intermediates (e.g., fructose-6-phosphate, fructose-1,6-bisphosphate, glyceraldehyde-3-phosphate, phosphoenol pyruvate). These compounds are research grade and are predominantly available in their neat form.

Methionine Cycle

The essential amino acid L-methionine (Met) is an important contributor to several metabolic pathways and plays a key role in many metabolic functions (e.g., epigenetics, detoxification, lipid membrane homeostasis). The Met cycle is closely linked to the folate metabolic pathway and is therefore indirectly tied to the physiological functions modulated by the folate cycle. Imbalance or abnormal functioning of the Met cycle has been reported to cause cancer, diabetes, and other systemic diseases. To help with biomarker assessment and the study into disease-related mechanisms, CIL offers a number of stable isotope-labeled Met cycle compounds (e.g., S-adenosyl-L-homocysteine or SAH, homocysteine, methionine). These materials are research-grade and available in their neat form.

TCA Cycle

The tricarboxylic acid (TCA) cycle, also known as the Krebs or citric acid cycle, plays an essential role in cellular metabolism. Its pathway comprises eight steps that involve a series of reactions starting with acetyl-CoA, the oxidative end product of the glycolysis pathway, and concluding with oxaloacetate. Biologically, the TCA cycle constitutes a major production source of cellular ATP and occurs in the mitochondrial matrix in eukaryotes or the cytoplasm in prokaryotes. To complement the qualitative/quantitative analysis of the TCA cycle in metabolomics- or metabolism-related initiatives, CIL is pleased to offer its intermediates (e.g., citrate, α-ketoglutarate, succinate, malate) and its side products (e.g., malonate, itaconate, methylcitrate) in their stable isotope-labeled form. These polar, central carbon metabolites are available in research grade as neat materials.

Tryptophan Pathway

The metabolism of the essential amino acid L-tryptophan (Trp) is an important driver of several physiological processes (e.g., immune response, neuronal function). Given its involvement in triggering immunity/inflammation and its impact on disease (e.g., cancer, neurodegeneration), researchers have targeted this pathway for the discovery of disease biomarkers and novel therapeutic targets. To aid this research, CIL offers several stable isotope-labeled metabolites of the Trp metabolism pathway. This encompasses the Trp precursor serotonin and a number of its pathway-centered products (e.g., kynurenine, anthranilic acid, tryptamine). These research-grade materials are available in various labeling patterns in their neat and/or solution form.

Urea Cycle

The urea cycle, also referred to as the ornithine or Krebs-Henseleit cycle, is essential to the removal of excess nitrogen as well as to the detoxification of ammonia. This pathway consists of five enzymatic reactions, with the first taking place in the mitochondrial matrix and the ensuing in the cytosol. Key intermediates of the cytosolic reactions are the amino acids – ornithine, citrulline, argininosuccinic acid, and arginine. Enzymatic deficiencies cause urea-cycle disorders (UCDs; e.g., ornithine transcarbamylase deficiency, argininosuccinate synthetase deficiency), with the intermediates serving as potential biomarkers for MS-based screening exercises. CIL is pleased to offer all four of these compounds in their stable isotope-labeled and/or unlabeled form as neat materials for use in exploratory or translational research applications.