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Figure 1
Demonstration of how increased flux can help resolve intermediate reaction species. (a) A histogram of turnover numbers compiled in the BRENDA enzyme database (https://www.brenda-enzymes.org). The median turnover number of 4.6 s−1 is shown and the range that includes 50% of all enzyme–substrate combinations about this median is also highlighted. (b), (c) and (d) Reaction coordinates for an example enzyme–substrate reaction with three intermediate species and a turnover time of approximately 200 ms (∼5.0 s−1 – the reaction scheme is shown at the bottom). The plots show which intermediates (ES1, ES2 and ES3) can be resolved with different detection snapshots: (b) 10 ms, (c) 1 ms and (d) 10 µs, simulating different fluxes of 1 × 1012, 1 × 1013 and 1 × 1015 photons s−1, respectively. The rate constant (k1, k−1, k2, k3, k4) values used to generate these curves were 104.4, 102.4, 103.4, 102.4 and 101.4, respectively.

IUCrJ
Volume 13| Part 2| March 2026| Pages 184-197
ISSN: 2052-2525
https://doi.org/10.1107/S2052252525011224