If you buy a Windows 10 Enterprise E3 or E5 User Subscription Licence through the Cloud Solution Provider (CSP) program then you need Windows 10 Pro Anniversary Edition on your device before the enterprise functionality can be enabled.
In January 2017 Microsoft relaxed the rules for the other devices (up to 4 more) that you might want to use: while they still need the Pro edition you can upgrade to Windows 10 free of charge from Windows 7 or Windows 8.1. What’s more, if you stop paying your subscription then ALL devices revert to Windows 10 Pro with perpetual use rights.
Windows 10 Enterprise is also part of Secure Productive Enterprise so these enhancements apply if you’re licensed for SPE E3 or E5 too.
See the Microsoft announcement here: http://bit.ly/2jOimqv.