MAGL — Monoacylglycerol Lipase

Identification and the 85 percent figure in vitro

Brain monoglyceride lipase was identified as the enzyme terminating 2-AG signalling by Dinh and colleagues in 2002. The quantitative share came five years later from activity-based protein profiling: Blankman, Simon and Cravatt resolved the brain enzymes capable of hydrolysing 2-AG and attributed approximately 85 percent of the activity to MAGL, with most of the remainder split between two alpha/beta-hydrolase-domain enzymes, ABHD6 and ABHD12. The 85 percent number is quoted constantly and worth understanding precisely: it is the share of hydrolytic activity in brain membrane and soluble fractions, not a claim that MAGL is the only route, and the residual 15 percent is part of why complete pharmacological silencing of 2-AG hydrolysis is difficult and why ABHD6 became a target in its own right.

Sources: Dinh TP 2002 · Blankman JL 2007

The arachidonic-acid consequence: one enzyme, two systems animal

This is the fact that makes MAGL structurally more interesting than "the 2-AG enzyme". Hydrolysing 2-AG does not merely end a cannabinoid signal; it liberates arachidonic acid, and in brain that arachidonic acid is a major feedstock for cyclooxygenase-2-derived prostaglandin synthesis. Nomura and colleagues showed in 2011 that MAGL is the principal source of the arachidonate pool driving neuroinflammatory prostaglandin production, and that MAGL blockade lowered brain prostaglandins and suppressed neuroinflammation in a parkinsonian model — with the anti-inflammatory effect substantially independent of cannabinoid receptors. So inhibiting MAGL pushes in two directions at once: up on 2-AG at CB1 and CB2, and down on the prostaglandin arm. It is, in effect, a cannabinoid agonist and a partial upstream NSAID sharing one mechanism. That dual action is the most compelling argument for MAGL as a drug target and also the reason its effects cannot be predicted from cannabinoid pharmacology alone.

• 2-AG hydrolysis is a major route to brain arachidonic acid, not just a signal-termination step.
• MAGL blockade therefore lowers prostaglandin production upstream of cyclooxygenase, without inhibiting the cyclooxygenase enzyme.
• Part of the anti-inflammatory effect in that work was not reversed by cannabinoid receptor antagonists — a receptor-independent arm.

Sources: Nomura DK 2011 · Blankman JL 2007

Tool compounds, named as reference points only animal

Three compounds anchor the literature and are named here so that potency claims elsewhere on the shelf have a scale to sit on. JZL184 is the O-hexafluoroisopropyl carbamate that made selective in-vivo MAGL blockade possible: Long and colleagues reported that it raised brain 2-AG roughly eight-fold and produced a subset of cannabinoid behavioural effects that were CB1-dependent. KML29 followed in 2012 as a more selective irreversible inhibitor bearing a hexafluoroisopropyl ketone, designed to reduce the FAAH cross-reactivity seen with high-dose JZL184. ABX-1431 is the compound that carried the mechanism into human trials as a clinical candidate for neurological indications. None of these is a botanical, a supplement or an available substance, and this shelf does not describe how any of them is made — they are cited so that a natural-product IC50 can be read against a known reference rather than in isolation.

Sources: Long JZ 2009 · Chang JW 2012 · Cisar JS 2018 · King AR 2009 · Tung MC 2021

What chronic complete blockade does: the argument against maximal inhibition animal

The single most important result on this page is negative. Schlosburg and colleagues dosed mice repeatedly with high-dose JZL184 and found that sustained, near-complete MAGL blockade did not sustain cannabinoid effects. Instead it produced functional antagonism of the endocannabinoid system: CB1 receptor desensitisation and downregulation in several brain regions, loss of the acute analgesic effect, cross-tolerance to exogenous cannabinoid agonists, and impairment of the endocannabinoid-dependent forms of synaptic plasticity that the system exists to mediate. Partial or intermittent inhibition did not produce the same collapse. The practical reading is that the ceiling described on the overview page protects you only while the enzyme is partially inhibited; drive it to completion and the receptor adapts, and the adaptation is in the direction opposite to the one intended. Anyone whose framing is "more inhibition is more tone" has the pharmacology backwards, and this is the paper that says so.

Sources: Schlosburg JE 2010 · Long JZ 2009

Natural MAGL inhibition, and the scale problem contested in vitro

The botanical MAGL inhibitors in the literature are pristimerin and euphol, both reversible and both reported by King and colleagues in a natural-product screen, and 8-prenylnaringenin from hops, reported from a pharmacophore screen plus in-vitro biochemical assays. Two honest qualifications belong with them. First, the 8-prenylnaringenin figure (IC50 approximately 9.5 µM) is roughly two orders of magnitude weaker than the nanomolar potencies reported for pristimerin, which makes the widely-repeated claim that 8-PN is "the most potent natural MAGL inhibitor" incorrect as stated. Second, every one of these numbers is an isolated-enzyme or cell-assay number. None of them establishes that any dietary or infusion exposure reaches the necessary concentration at the enzyme in a person. That gap is treated as its own section on the natural-inhibitors page because it is the whole difference between a research reference and supplement copy.

Contested — caveat. The comparative potency ranking rests on IC50 values measured in different laboratories with different assay formats and enzyme sources; cross-paper IC50 comparison is indicative, not quantitative. The exact King et al. potency figures were not independently re-measured for this entry.

Sources: King AR 2009 · Tung MC 2021