Broccoli Sprout Myrosinase.

Myrosinase is the thioglucosidase that hydrolyses glucoraphanin into sulforaphane, and glucoraphanin is inert until that bond is cut. Neither delivers the isothiocyanate on its own.

Most standardised sprout extracts are processed in ways that inactivate native myrosinase, leaving glucoraphanin that depends on gut bacteria for conversion. Adding active myrosinase restores the hydrolysis step in the upper gut.

Sulforaphane is what myrosinase produces from glucoraphanin, so the two sit either side of one reaction. Supplying preformed sulforaphane bypasses the need for the enzyme.

Myrosinase hydrolyses the whole glucosinolate class at the common thioglucoside bond. Any glucosinolate in the formula is a substrate for it.

Myrosinase converts sinigrin into allyl isothiocyanate, the pungent mustard compound. Without the enzyme sinigrin stays intact.

Glucotropaeolin is hydrolysed by myrosinase to benzyl isothiocyanate. The glucosinolate is the storage form and the enzyme is the trigger.

Myrosinase converts gluconasturtiin into phenethyl isothiocyanate. Conversion is the whole point of pairing the two.

Myrosinase hydrolysis of glucobrassicin yields indole-3-carbinol, which condenses further under stomach acid. The indole route depends on the same enzymatic first step.

AITC is the product myrosinase generates from sinigrin. Supplying it directly removes the conversion step.

DIM forms when indole-3-carbinol, itself a myrosinase product of glucobrassicin, dimerises in acid. The enzyme sits two steps upstream of DIM.

Ascorbate acts as a cofactor for plant myrosinase and raises the rate of glucosinolate hydrolysis at physiological concentrations. Formulators include it for that reason as well as for its own account.

Myrosinase converts glucoraphanin into sulforaphane, and sulforaphane raises transcription of antioxidant response element genes. Several of the downstream enzymes in that set, including glutathione peroxidases and thioredoxin reductase, are selenoproteins that cannot be assembled without selenium. Low selenium status therefore caps part of the response that the enzyme step makes possible. This is a cofactor relationship, not a measured combination outcome.

Sulforaphane released by myrosinase is conjugated to glutathione by glutathione S-transferases and then travels the mercapturic acid pathway. Glutathione is a tripeptide of glutamate, cysteine and glycine, so all three amino acids sit upstream of that handling step. Glycine is the least rate-limiting of the three in most diets, which is worth saying plainly rather than overselling the pairing.

The glutathione pool that conjugates isothiocyanates is normally limited by cysteine availability rather than by glycine or glutamate. Where cysteine supply is low, the conjugation and export route for sulforaphane has less capacity. The relationship is textbook amino-acid biochemistry and does not rest on a combination trial.

N-acetylcysteine is deacetylated to cysteine and used for glutathione synthesis, the same pool that conjugates sulforaphane. Formulators pair thiol donors with sprout material for that reason. Worth noting the direction is one-way support of a conjugation step, not an increase in how much sulforaphane the enzyme produces.

Isothiocyanates react with the thiol group of glutathione, which is how the body escorts them out. Adding glutathione alongside a myrosinase-active product changes the distribution of the isothiocyanate between free and conjugated forms rather than adding to the amount made. Whether oral glutathione meaningfully reaches tissue thiol pools is a separate and unsettled question.

When myrosinase has been destroyed by heat, colonic bacteria perform some of the same hydrolysis, though less efficiently and with wide person-to-person variation. Supplying an active enzyme and supplying converting bacteria are two routes to the same product, so they overlap rather than stack cleanly. Composition of the resident microbiota is the main reason two people given identical glucoraphanin show different isothiocyanate recovery.

Myrosinase is a glycoprotein and loses activity on exposure to gastric acid and proteases, which is why delayed-release shells and dry, low-moisture blends are used. Enzyme blends intended to work in the stomach sit in a different pH window than a myrosinase meant to survive to the small intestine. Combining them in one capsule is a formulation choice with real trade-offs, not a synergy claim.

Alpha-lipoic acid and sulforaphane both influence the Keap1 and Nrf2 antioxidant response element axis, by different chemistry: lipoic acid through thiol redox cycling, sulforaphane through covalent modification of Keap1 cysteines. The overlap is mechanistic and measured mostly as marker changes rather than outcomes. Myrosinase contributes here only as the step that makes the sulforaphane available.

Curcumin is another electrophile described as modifying Keap1 cysteine residues, so it acts on the same signalling node sulforaphane does. Products often combine them for that reason. The evidence for the pair is mechanistic and marker-level, and it says nothing about myrosinase activity itself.

Plant polyphenols, including catechins, are described as inhibitors of myrosinase in enzymology work, and tannins are a known interferent in myrosinase assays. A high-polyphenol matrix in the same capsule or the same sip of water is therefore a plausible drag on the conversion step. This is an anti-synergy worth flagging rather than a reason to avoid either ingredient.

Ascorbate is the classical cofactor of plant myrosinase and accelerates hydrolysis of glucosinolates at low millimolar levels, while higher concentrations slow the same reaction. Direction depends on concentration, so more is not simply more. The biphasic behaviour is a settled feature of the enzyme, described in enzymology rather than in a supplement trial.