Catalyzes the interconversion of N-acetylglucosamine to N-acetylmannosamine. Binds to renin forming a protein complex called high molecular weight (HMW) renin and inhibits renin activity. Involved in the N-glycolylneuraminic acid (Neu5Gc) degradation pathway. an N-acyl-D-glucosamine = an N-acyl-D-mannosamine Amino-sugar metabolism; N-acetylneuraminate degradation. Homodimer. Kidney, adrenal gland, brain, lung, spleen, ovary, testis and heart. Belongs to the N-acylglucosamine 2-epimerase family. It is uncertain whether Met-1, Met-2 or Met-12 is the initiator. Truncated N-terminus.