A rapid spectrophotometric assay for ferrochelatase activity in preparations containing much endogenous hemoglobin and its application to soybean root-nodule preparations
✍ Scribed by R.J. Porra
- Publisher
- Elsevier Science
- Year
- 1975
- Tongue
- English
- Weight
- 481 KB
- Volume
- 68
- Category
- Article
- ISSN
- 0003-2697
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✦ Synopsis
A simple and rapid spectrophotometric assay for ferrochelatase (EC 4.99.1.1) activity is described which is suitable for use with enzyme preparations containing large amounts of hemoglobin. In this method mesoporphyrin IX is used as substrate and the product, mesoheme IX, is measured by recording the reduced minus the oxidized pyridine hemochrome spectrum. Pyridine mesohemochrome has an c~ peak at 547 nm and a trough at 531 nm while the c~ peak and trough of pyridine protohemochrome (from hemoglobin) are at 557 and 541 ram, respectively. 547 531 nm be Thus the contribution of the protohemochrome to El e m , which can allowed for, is small, and so the method gives very reliable determinations of the amounts of mesoheme IX formed.
By means of this assay, it was shown that in excess of 90% of the ferrochelatase activity of soybean root-nodules is present in the bacteroid cells and less than 10% in the plant mitochondria: No ferrochelatase activity could be detected in the soluble plant fraction.