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 Optimum pH is 6.8. Optimum temperature is 47 degrees Celsius. Amino-sugar metabolism; N-acetylneuraminate degradation. Homodimer. Kidney, liver, adrenal, and pituitary glands the amount being much greater in kidney than in the other tissues. Belongs to the N-acylglucosamine 2-epimerase family.