What are the structural differences among LDH isoforms, and how do they affect their function?

Lactate dehydrogenase (LDH) consists of five distinct isoforms that differ in the ratio of H (heart) and M (muscle) subunits present in their tetrameric structure. LDHA predominantly favors lactate production and is not inhibited by high concentrations of pyruvate, while LDHB favors pyruvate production. These structural differences influence their enzymatic activity and functional roles in various tissues.