What's The 'L' stand for my culinary com padre?
Origially, "L" meant levorotatory, if you really want to know. It's the "handedness" (left/right) of the molecule. The l- enantiomer (or isomer, or form, lower case here) is defined as the form that rotates the plane of polarized light passing through it counter-clockwise... The d form (dextrorotatory) the other way... For amino acids like tryptophan, capital L and D refer now to the absolute stereochemistry and not the direction of rotation of polarized light.
Put more succinctly, L-amino acids are the natural ones that make up a significant portion of that turkey you just ate.
May the magic of tryptophan sprinkle it's self over your day MAFF
It's "L" Tryptophan, the L variety of this enzyme is the one that knocks you out
Technically it's not an enzyme... it's an amino acid (and a precursor to serotonin...)
Happy Turkey Eating!