An Enzyme-bound Red Chlorophyll Catabolite from Enzymatic Oxygenation of Pheophorbide

An Enzyme-bound Red Chlorophyll Catabolite from Enzymatic Oxygenation of Pheophorbide a 

PaO is intriguingly specific for Pheo a (5a) and is located in the chloroplast envelope. It catalyzes the remarkable transformation of 5a into (a bound form of) RCC (11) (5). Besides the incorporation of two oxygen atoms, the ring opening at the newly oxygenated sites appears to achieve, all in this step, the formation of two carbonyl functions and the saturation of the eastern (3-meso position. The mechanism of the hypothetical isomerization of the primary enzymatic oxygenation product to the ring-opened (enzyme-bound form of) 11 has not been clarified. 

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