The heme synthetase step in human bone marrow has been characterized in a crude lysate as an enzymatic reaction in that it has a pH optimum of 7.4, is heat labile, and at optimum substrate concentrations is linear with time and enzyme concentration over the first 30 minutes. The Km of iron was found to be 1.7 x 10-5M and for protoporphyrin 1.8 x 10-6M.

High iron concentrations do not affect the enzyme but ascorbic acid and glutathione were found to augment the activity of the enzyme. Pyridoxine and high protoporphyrin concentrations inhibit heme synthetase activity. A negative feedback control of heme synthetase by heme is present in human red cell precursors.

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© 1968 by American Society of Hematology, Inc.
1968
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