Conversion of chlorophyll b to chlorophyll a via 7-hydroxymethyl chlorophyll.
Chlorophyll b is synthesized from chlorophyll a by the oxidation of the methyl group on the ring B of the tetrapyrrole ring to the formyl group. Previously, we reported that chlorophyllide b could be converted to chlorophyll a in isolated cucumber etioplasts indicating the conversion of chlorophyll b to chlorophyll a. To identify the intermediate molecule, we used barley etioplasts instead of cucumber. Chlorophyll a and an additional pigment were found after incubation of chlorophyllide b with isolated barley etioplasts. The pigment has the same retention time and absorption spectrum as 7-hydroxymethyl chlorophyll, which has the hydroxymethyl group on ring B instead of the formyl group of chlorophyll b. Authentic 7-hydroxymethyl chlorophyll was prepared by reduction of chlorophyll b by NaBH4. Chlorophyll a accumulated during the incubation of 7-hydroxymethyl chlorophyllide with etioplasts. These findings indicate that chlorophyll b is converted to chlorophyll a via 7-hydroxymethyl chlorophyll. Chlorophyll b and 7-hydroxymethyl chlorophyll accumulated within a short period of incubation of chlorophyllide b with etioplasts. However, chlorophyll a accumulated with a concomitant decrease of chlorophyll b and 7-hydroxymethyl chlorophyll. These observations also suggest that chlorophyll b is converted to 7-hydroxymethyl chlorophyll and then to chlorophyll a. Both steps required ATP.
Ito
H
H
Department of Botany, Faculty of Science, Kyoto University, Japan.
Ohtsuka
T
T
Tanaka
A
A
D002250:Carbon Radioisotopes; D002734:Chlorophyll / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism / Q000031:analogs & derivatives; D000077194:Chlorophyll A; D002851:Chromatography, High Pressure Liquid; D001467:Hordeum; D007700:Kinetics; D010860:Pigments, Biological; D011865:Radioisotope Dilution Technique; D013053:Spectrophotometry; D013997:Time Factors
C098029:7-hydroxymethyl chlorophyll; D002250:Carbon Radioisotopes; D010860:Pigments, Biological; D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A