Chlorophyllase

The early stages of catabolism correspond to the replacement of Mg by two H atoms under acidic conditions and/or by the action of Mg-dechelatase and the cleavage of the phytol chain by the enzyme chlorophyllase. The still greenish intermediates are pheophytins, chlorophyUides, and pheophorbides with intact tet-rapyrrole rings. - ... 

Roca, M. and Mmguez-Mosquera, M.L, Involvement of chlorophyllase in chlorophyll metabolism in olive varieties with high and low chlorophyll content, Physiol. Plant, 117, 459, 2003. 

Degreening of peel has been related to chlorophyllase activity. Barmore (14) demonstrated that chlorophyllase activity in peel increased following treatment of fruit with ethylene. 

Figure 9.37 Chemical structures of chlorophylls-a and b which contain a propionic acid esterified to a C20 phytol chlorophylls-cj and C2 have an acrylic acid that replaces the propionic acid. Also included are the pheopigments, the four dominant tetrapyrrole derivatives of chloropigments (pheopigments) found in marine and fresh-water/estuarine systems (chlorophyllide, pheophorbide, pheophytin, pyropheophorbide.) More specifically, chlorophyllase-mediated de-esterification reactions (loss of the phytol) of chlorophyll yield chlorophyllides. Pheophytins can be formed when the Mg is lost from the chlorophyll center. Pheophorbides are formed from removal of the Mg from chlorophyllide or removal of the phytol chain from pheophytin, and pyrolyzed pheopigments, such as pyropheophorbide and pyropheophytin, are formed by removal of the methylcarboxylate group (-COOCH3) on the isocylic ring from the C-13 propionic acid group.

Except for the slower demise of chlorophyl1-c, the alteration of chlorophyll-a during senescence and death can be attributed to cellular decompartmentalization and resultant action of cellular acids (Mg-loss) and enzymes (e.g chiorophyllase, phytol loss, 35) The relative amounts of pheophytin-a versus pheophorbide-a resulting from senescence-death has been shown to be species specific and is related to chlorophyllase activity (37). Sediment Trap Samples. The alteration of chlorophyll due to senescence/death phenomena, described above, yield a certain suite of pigments. Such arrays, dominated by pheophytin-a, might be expected to form the precursor complement in sediments deposited in an environment free of consumers. Such is obviously not the case in nature. Since the vast majority (e.g. 95-99%) of primary production serves as fodder in marine food webs (38) we must consider heterotrophic alteration of detrital tetrapyrrole pigments. 

No phytol-free pigments were detected in green beans. In the same study, chlorophyllase activity was induced in unheated cucumbers by holding them in 7.5% sodium chloride solution at room temperature. 

Figure 3. Chlorophyllase activity expressed as percent conversion of chlorophyll to chlorophyllide, In spinach during growth (solid line) and after storage at 5°C (broken line).

Commercial production of the pigments in England was described by Humphrey (49). Chlorophyll is extracted from dried grass or alfalfa with acetone or chlorinated hydrocarbons. Sufficient water is added, depending on the moisture of the plant material, to aid in penetration of the solvent while avoiding activation of chlorophyllase enzyme. Pheophytin may be acid hydrolyzed before copper ion is added resulting in the formation of water soluble copper chlorophyllin. 

The structure of //v-NCC- l (2) was consistent with the loss of the phytol side chain from Chi a (la) as an early event of Chl-breakdown. The enzymatic hydrolysis of Chi a (la) to chlorophyllide a (3a) and to phytol by chlorophyllase was discovered in the early 20th century by A. Stoll (see Scheme 3) (30). Chlorophyllase removes the lipophilic phytol anchor of the Chl-molecules, which is crucial for binding of the... 

Willstatter R, Stoll A (1913) Die Wirkungen der Chlorophyllase. Untersuchungen iiber Chlorophyll, p. 172. Julius Springer, Berlin... 

Matile P, Schellenberg M, Vicentini F (1997) Localization of Chlorophyllase in the Chloroplast Envelope. Planta 201 96... 

Jacob-Wilk D, Holland D, Goldschmidt EE, Riov J, Eyam Y (1999) Chlorophyll Breakdown by Chlorophyllase Isolation and Functional Expression of the Chlasel Gene from Ethylene-treated Citrus Fruit and Its Regulation During Development. Plant J 20 653... 

Tsuchiya T, Ohta H, Okawa K, Iwamatsu A, Shimada H, Masuda T, Takamiya K-I (1999) Cloning of Chlorophyllase, the Key Enzyme in Chlorophyll Degradation Finding of a Lipase Motif and the Induction by Methyl Jasmonate. Proc Natl Acad Sci USA 96 15362... 

Chlorophyllase is an intrinsic membrane glycoprotein situated in the thylakoid membrane (Terpstra, 1981). It does not normally interact with its chlorophyll substrate, although chlorophyll is situated in the same membrane. In intact plant tissue, chlorophyllase is kept in an inactive and stable conformation by the adjacent lipids of the thylakoid membrane (Lambers and Terpstra, 1985). In order to activate chlorophyllase, a substantial disruption of the thylakoid membrane has to... 

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