The substrate analogue S-adenosyl-l-homocysteine (SAH) was co-crystallised with SAM hydroxide adenosyltransferase from Pyrococcus horikoshii. Of the two active site water molecules one appears to be structural and the other is a candidate for nucleophilic attack, to become the C5′ adenosyl hydroxyl group. The data support a mechanism in which the Arg–Asp ion pair is important for positioning both water molecules.
Bibliographical noteFunding Information
BBSRC. Grant Number: BB/F007426/1 and BBS/B/14426
NIH. Grant Number: CA127622
Scottish Funding Council
- enzyme catalysis