One such family of enzymes are archaeal prenyltransferases including geranylgeranylglyceryl phosphate synthases (GGGPSs or G3PSs). These enzymes construct membrane lipids with ether bonds, which constitute the primary biochemical distinction between archaea and bacteria. Compared to ester lipids, ether lipids possess increased hydrolytic stability, which has allowed archaea to conquer some of the most extreme environments on earth, such as deep-sea thermal vents. To furnish these ether lipids, G3PSs natively react electrophilic geranylgeranyl pyrophosphate (1) with nucleophilic glycerol phosphate (GP, Figure ). Since the resulting large prenyl ethers are structurally far removed from typical products of (engineered) methyltransferases, G3PSs would be valuable additions to the biocatalytic alkylation toolbox to make a range of useful products which are otherwise inaccessible through biocatalysis. Indeed, glycerol ethers find a variety of ). As AfG3PS operates without observable side reactions, has a half-life of >>10 10 years and its substrates are stable, the theoretical total turnover number of AfG3PS is >>10 and conversion (given some level of trace activity) will be quantitative for any substrate. Thus, rate and affinity are the relevant metrics. f) Orthogonal to kinetic experiments, substrate binding by AfG3PS can be assessed by tryptophan fluorescence or with dye-labelled enzyme. Please see the Supplementary Information for experimental details and the externally hosted supplementary material for all raw data. applications, 24 e.g. as surfactants, emulsifiers, and bioactive ingredients. Prenyl ethers, specifically, are also known for their pleasant flowery and/or fruity scents (a trait we can confirm does extend to prenyl glycerides derived from dephosphorylated G3PS products) and have potential applications in cosmetics and perfumes. Nonetheless, any synthetic applications and/or engineering of G3PSs to enable access to these and other useful products necessitates i) a fundamental understanding of how these enzymes operate as well as ii) a methodological repertoire for their examination. However, despite their important evolutionary role and potential synthetic uses, literature reports on G3PSs are relatively scarce. As such, our present understanding of these enzymes is limited, particularly regarding their ability to bind and convert pyrophosphates other than 1 as well as their selectivity and the mechanism of etherification (please see the supplementary information for a more detailed review and discussion of the literature).