Cardiovascular disease. Another 2018 overview indicates that top levels of BCAAs may be a marker for heart ailments.Five enzymes engage in the parallel synthesis pathways for isoleucine, valine, and leucine: threonine dehydrogenase, acetohydroxyacid synthase, ketoacid reductoisomerase, dihydroxyacid dehydrogenase and aminotransferase.[three] Threon