Final answer:
In the Golgi complex, the sugar mannose is typically removed from the N-linked core oligosaccharide chains on proteins during their processing, which is different from the trimming of glucose residues that occurs in the ER.
Step-by-step explanation:
The sugar usually removed from N-linked core oligosaccharide chains on proteins in the Golgi complex, as opposed to the glucose residues trimmed off in the endoplasmic reticulum (ER), is mannose. In the Golgi apparatus, the complex process of protein glycosylation continues after initial modifications in the ER. The Golgi complex, specifically through the actions of glycosidases and glycosyltransferases, elaborates and refines these glycan structures by adding or subtracting individual sugar units.
Different types of oligosaccharides, such as N-glycans, start their assembly within the rough endoplasmic reticulum. As glycoproteins transit to the Golgi apparatus, they are further processed, which involves an enzymatic trimming of specific sugar moieties. Mannose is often the sugar that is selectively removed during the maturation process of the glycoprotein within the Golgi, particularly in the medial Golgi cisternae. The alteration of glycan chains plays a crucial role in dictating the final structure and function of glycoproteins, which, after complete processing, are transported to their final extracellular or membrane destinations.
This elaborate process of glycosylation and the function of the Golgi apparatus are crucial for the proper functioning and stability of glycoproteins, influencing diverse biological processes including cell-cell recognition, protein sorting, and receptor activation. Grounded in this cellular mechanism are potential implications for various diseases and therapeutic interventions.