The best replacement for active site is binding site.

The best alternatives to active site are rated as following:
★★★★★  binding site
★★★★★  allosteric site
★★★  regulatory site
★  substrate binding site
★  substrate

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Speaking about active site, one probably shouldn't forget about substrates.

Other search terms related to active site and their ratings are:
★★★★★ substrates
You have in mind a companion for active site and it is not yet here? Propose!



Google Trends

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active site
binding site
allosteric site