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Where are sulfate groups added to proteins in the Golgi apparatus?

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Diagram of the Golgi apparatus showing its stacked, curved membranes with labeled parts including cisternae, cis face, trans face, lumen, and various vesicles involved in cellular transport and secretion. — Golgi apparatus A membrane-bound organelle of eukaryotic cells, the Golgi apparatus is made up of a series of flattened, stacked pouches called cisternae that function as a series of compartments that progressively refine and direct cellular products to their proper destinations. .

In the Golgi apparatus, the addition of sulfate groups to proteins occurs primarily in the trans cisternae.1

The Golgi apparatus is a highly organized, polarized organelle where distinct enzymatic reactions take place within specific compartments. While the cis and medial cisternae are primarily responsible for processes such as the removal of mannose moieties, the trans cisternae are the site for the addition of galactose or sulfate.1