# Synthases vs Lyases - nomenclature

Lyases are a class of enzymes that break down (lyase: ly- = lysis, -ase = enzyme) bonds like $$\ce{C-C, C-S}$$ and so on (except hydrolysis), and can eliminate molecules like $$\ce{H2O}$$ or $$\ce{CO2}$$. They are referred to as synthases, respectively, some authors categorize synthases among lyases.

My question is, (if word "synthesis" still means joining two substances into one more complex by creation of bonds between them), why are synthases placed among lyases if lyases actually break down bonds and synthases are (by their name) supposed to join, create bonds? Respectively, why was their name derived from 'synthesis' if their role actually is to break down?

Lastly I have even seen that JCBN (Joint Commission on Biochemical Nomenclature) dictated that "synthase" may be used for any enzyme catalysing synthesis, and that even without paying attention to whether the enzyme uses NTP like ATP (ligases = synthetases) or not (synthases).

I'd like to let everybody know that I understand the difference between synthases and synthetases, and that this difference isn't my point of question. I also do not controvert the fact that in the literature synthases are referred to as lyases, but somehow I kind of miss logic of naming enzymes responsible for breakdown after 'synthesis' which is actually opposite reaction than analysis. Until today I thought 'synthesis' stands for joining (syn-) and 'analysis' for breakdown into simpler products.

Here I attach in the images the answers from Wikipedia and forums for you to read.

• Wikipedia says: Lyase catalyses breaking, elimination. And synthase catalyses synthesis process. – Diana51 Jun 14 at 15:37