Over 50 years ago it was hypothesized that enzymes responsible for catalyzing sequential reactions in a metabolic pathway are organized in supramolecular complexes termed metabolons.
Biochemical reactions underlying metabolic functions in cells are generally well understood, however, little is known about the cellular organization of the enzymes in a given pathway. Rather than being a ‘bag of enzymes’ where enzymes freely diffuse, recent advances suggest that the cytoplasm is highly organized, composed of cytoskeleton and internal compartments.
We study how enzymes responsible for catalyzing sequential reactions in a metabolic pathway are organized. Do they self-assemble stochastically into clusters? Are they assisted by scaffolding proteins or chaperones, tailored to induce higher order building blocks? Or are they dynamically orchestrated in microenvironments through transient interactions?
The glucosinolate biosynthetic pathway in Arabidopsis thaliana as an ideal model system of a multi-step pathway as we know all the enzymes, we know that intermediates are efficiently channeled even between organelles, and for Arabidopsis, highly advanced transcriptomics and proteomics databases as well as mutant collections are available.
We study the composition of the proposed enzyme clusters by screening for scaffolding proteins and assembly chaperones, employing complementary untargeted approaches such as co-expression, yeast-2-hybrid, co-immuno-precipitation, and proteomics.
Understanding how physical interactions of proteins in enzyme clusters determine the metabolic outcome of the pathway is a prerequisite for subsequently studying the impact of the dynamics of enzyme clusters on metabolic flux.
Ultimately, our goal is to understand how the pathway assembly /disassembly is orchestrated in response to external and developmental cues, and how the pathway is connected to other pathways in the metabolic grid.
Bassard J-E, Halkier BA (2017) How to prove the existence of metabolons? Phytochem Rev. 17, 211–227.
Nintemann SJ, Vik D, Svozil J, Bak M, Baerenfaller K, Burow M, Halkier BA (2017) Unravelling protein-protein interaction networks linked to aliphatic and indole glucosinolate biosynthetic pathways in arabidopsis. Front Plant Sci 8:2028. DOI: 10.3389/fpls.2017.02028