Fatty acid binding of myoglobin depends on its oxygenation

In the present work we show with different binding assays chicken gizzard myoglobin is able to bind fatty acids and bromosulphophthalein (BSP) in vitro. The fatty acid binding depends on the oxygenation of the myoglobin. Freshly prepared chicken gizzard, chicken or bovine heart myoglobin have a high fatty acid binding capability. However, when oxy-myoglobin in converted to met-myoglobin by dialysis against acidic buffer at high ionic strength (or when commercially available myoglobins are used) a 60-70% lower fatty acid binding capacity is found. Like bovine serum albumin (BSA), gizzard myoglobin has the highest affinity for unsaturated fatty acids and a lower affinity for saturated fatty acids or dyes. Chicken gizzard smooth muscle myoglobin may function as an additional fatty acid binding protein in vivo.