IUBMB Enzyme Nomenclature


Accepted name: magnesium dechelatase

Reaction: (1) chlorophyll a + 2 H+ = pheophytin a + Mg2+
(2) chlorophyllide a + 2 H+ = pheophorbide a + Mg2+

For diagram of reaction click here.

Other name(s): SGR (gene name); SGRL (gene name); Mg-dechelatase

Systematic name: chlorophyll a magnesium lyase

Comments: Inhibited by Ca2+, Mg2+ and especially Hg2+. SGR has very low activity with chlorophyllide a and none with chlorophyll b. It acts on chlorophyll a both in its free form and in protein complex. SGRL, on the other hand, is more active with chlorophyllide a than with chlorophyll a. The magnesium formed is scavenged by MCS (metal-chelating substance).

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Tang, L., Okazawa, A., Fukusaki, E. and Kobayashi, A. Removal of magnesium by Mg-dechelatase is a major step in the chlorophyll-degrading pathway in Ginkgo biloba in the process of autumnal tints. Z. Naturforsch. C 55 (2000) 923-926. [PMID: 11204197]

2. Costa, M.A., Civello, P.M., Chaves, A.R. and Martínez, G.A. Characterization of Mg-dechelatase activity obtained from Fragaria x ananassa fruit. Plant Physiol. Biochem. 40 (2002) 111-118.

3. Wang, T., Quisenberry, S.S., Ni, X. and Tolmay, V. Enzymatic chlorophyll degradation in wheat near-isogenic lines elicited by cereal aphid (Homoptera: Aphididae) feeding. J. Econ. Entomol. 97 (2004) 661-667. [PMID: 15154496]

4. Suzuki, T., Kunieda, T., Murai, F., Morioka, S. and Shioi, Y. Mg-dechelation activity in radish cotyledons with artificial and native substrates, Mg-chlorophyllin a and chlorophyllide a. Plant Physiol. Biochem. 43 (2005) 459-464. [PMID: 15890522]

5. Kunieda, T., Amano, T. and Shioi, Y. Search for chlorophyll degradation enzyme, Mg-dechelatase, from extracts of Chenopodium album with native and artificial substrates. Plant Sci. 169 (2005) 177-183.

6. Shimoda, Y., Ito, H. and Tanaka, A. Arabidopsis STAY-GREEN, Mendel’s green cotyledon gene, encodes magnesium-dechelatase. Plant Cell 28 (2016) 2147-2160. [PMID: 27604697]

[EC created 2017]

Return to EC 4.99.1 home page
Return to EC 4.99 home page
Return to EC 4 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page