What makes Sockeye salmon sweet?

Tonight I cooked sockeye (bloody expensive over here) salted both sides (cornish sea flakes) added a drizzle of olive oil, let it sit for about an hour in the fridge in its bag, …butter for the pan finish, wife was ecstatic (as was I) she normally leaves the skin (philistine) but not tonight, all gone with relish.

Handling the firmer flesh was a breeze, as was pan turning, no sugar added, as barely touched as could be but oh so sweet! can someone offer me some context here please, i’m stumped

Glycine. Glycine, is a aminon acid/protein, with a sweet taste, that the sockeye flesh poses. Have a sweet supper/life!

Thanks, will now go and look at its construct / building blocks, shame farmed salmon doesnt have this it would be a lot more popular, but thats the difference.