Catalyzes the cleavage of N-acetylneuraminic acid (sialic acid) to form pyruvate and N-acetylmannosamine via a Schiff base intermediate (PubMed:33895133). It prevents sialic acids from being recycled and returning to the cell surface (PubMed:33895133). Involved in the N-glycolylneuraminic acid (Neu5Gc) degradation pathway (PubMed:22692205, PubMed:33895133). Although human is not able to catalyze formation of Neu5Gc due to the inactive CMAHP enzyme, Neu5Gc is present in food and must be degraded (Probable).
