Although features of a SKU can be edited (for example, Retail Price, Safety Stock, and other attributes), an Item’s SKU and Description values cannot be modified. (Physical Inventory values associated with any stocked SKU must be preserved.)
If you require a SKU change:
Create a SKU with the new SKU or Description.
Discontinue the original SKU as needed.
Inventory can be "transferred" to the new item via a shipment and self-supplied ASN, as needed.