synthetase

The story

1. Proto-Indo-European*ḱe?
2. Proto-Indo-European*ḱómder.?
3. Proto-Indo-European*sem-der.?
4. Proto-Hellenic*ksún
5. Ancient Greekσύν (sún)
6. Ancient Greekσυν- (sun-)
7. Proto-Indo-European*dʰeh₁-
8. Proto-Indo-European*dʰédʰeh₁ti
9. Ancient Greekτίθημι (títhēmi)
10. Ancient Greekσῠντῐ́θημῐ (sŭntĭ́thēmĭ)
11. Ancient Greekσύνθεσις (súnthesis)
12. Latinsynthesis
13. Englishsynthesis
14. Proto-Indo-European*dwóh₁
15. Proto-Indo-European*trísinflu.
16. Proto-Indo-European*dwís
17. Ancient Greekδιά (diá)
18. Ancient Greekδῐᾰ- (dĭă-)
19. Proto-Indo-European*steh₂-
20. Proto-Indo-European*stísteh₂ti
21. Proto-Hellenic*hístāmi
22. Ancient Greekῐ̔́στημῐ (hĭ́stēmĭ)
23. Ancient Greekδῐῐ̈́στημῐ (dĭĭ̈́stēmĭ)
24. Ancient Greekδῐᾰ́στᾰσῐς (dĭắstăsĭs)
25. Englishdiastase
26. English todaysynthetase

From synthesis + -ase.