Erythroid 5-aminolaevulinate synthase activity during normal and iron deficient erythropoiesis

Reduced erythroblast 5-aminolaevulinate (ALA) synthase activity was observed during iron/haem deficient erythropoiesis. Enzyme activity was reduced approximately threefold to levels similar to those previously detected during sideroblastic erythropoiesis. This response would appear to be erythroblast specific as haem deficiency is known to stimulate hepatic ALA synthase activity. It is, however, unclear as to whether this reduced enzyme activity relates to iron deficiency or to the consequent haem deficiency.