Complex sentence: Sulfation, performed by carbohydrate sulfotransferases, generates carbohydrate sulfate esters, which are only located extracellularly, whether through excretion into the extracellular matrix or by presentation on the cell surface.
Split into simpler sentences: Sulfation, performed by carbohydrate sulfotransferases, generates carbohydrate sulfate esters. These sulfate esters are only located extracellularly, whether through excretion into the extracellular matrix (ECM) or by presentation on the cell surface.