Canola contains large amounts of sulphur. Sulphur is part of structural and enzymatic components. Sulphur is a key component of two essential amino acids (cysteine and methionine) and is needed for protein synthesis. Chlorophyll synthesis also requires sulphur. Both of these amino acids are also precursors for coenzymes and secondary plant substances. Glutathione, an important antioxidant in plants and animals, is synthesized from cysteine. Glutathione contents are higher in leaves than roots. It’s found primarily in the chloroplasts where its anti-oxidant ability is needed to detoxify free radicals generated during photosynthesis. Glutathione also functions as transient sulphur storage, and a precursor of phytochelatins (compounds which detoxify heavy metals in plants). Thioredoxins, another important group of sulphur compounds related to glutathione, help activate several enzymes in carbon metabolism. Sulphur also is part of several enzymes and coenzymes such as ferrodoxin, biotin (vitamin H), coenzyme A, urease, and thiamine (vitamin B1).An important group of secondary plant sulphur compounds in canola are glucosinolates. Plants contain over 100 different glucosinolate compounds. These secondary compounds, although not well understood, probably have a number of functions. Glucosinolates are stored in cell vacuoles, and can be broken down by an enzyme (myrosinase) to yield glucose, sulphate and volatile compounds such as isothiocyanate. Glucosinolates contribute to defense or attractant systems for certain insects and diseases. When plant cells are destroyed by insect feeding, glucosinolates are broken down, releasing various deterrents/attractants.Glucosinolate levels are highest in growing points, roots, and youngest leaves, all of which are most vulnerable to insects and diseases. The role of glucosinolates as sulphur reserves to maintain plant sulphur during periods of high demand (such as bolting, flowering, podding and seed fill) is controversial. However, research in Europe showed that glucosinolates comprised a small sulphur pool in leaves, and under induced sulphur deficiency, sulphate (SO4-2) mobilization from storage in cell vacuoles was about 10 times greater than contributions from glucosinolates.Sulphur is also a constituent of sulpholipids, which are membrane components.