Latent phenolase in extracts of broad-bean (<i>Vicia faba</i> L.) leaves. Activation by acid and alkali

Kenten, R. H.

doi:10.1042/bj0670300

Cited by 117 publications

(60 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar phenomena of the activation of polyphenoloxidase have been reported: the enzymein a water extract from broad bean leaves is activated by an acid or base shock, 12) or by treatment with anionic detergents, such as sodium dodecyl sulfate (SDS).13) The enzymes from sugar beets, spinach, grapes, and Slices of potatoes and apples also darkned rapidly after pressurization. Therefore, farther experiments were done to find whether plant polyphenoloxidases are generally activated by pressure or SDStreatment.…”

Section: Activitymentioning

confidence: 73%

Activation of Polyphenoloxidase in Pear Fruits by High Pressure Treatment.

Asaka

Hayashi

1991

Agricultural and Biological Chemistry

View full text Add to dashboard Cite

Section: Activitymentioning

confidence: 73%

Activation of Polyphenoloxidase in Pear Fruits by High Pressure Treatment.

Asaka

Hayashi

1991

Agricultural and Biological Chemistry

View full text Add to dashboard Cite

“…Spinach polyphenol oxidase can be activated with trypsin, but the nature of the activation process is unclear since it occurred even with denatured trypsin preparations (27). Activation of broad bean catechol oxidase by detergents, acid, alkali, chaotropic, or denaturing agents (12,22,26) has been attributed to conformational changes in the enzyme (22, see also Ref. 14).…”

Section: Resultsmentioning

confidence: 99%

“…Activation can be achieved by treating extracts or membranes with detergents (16), acid or alkali (12), denaturing agents (22), or with proteolytic enzymes such as trypsin (27) or trypsin plus carboxypeptidase a (19). In many cases, the enzyme is activated upon release from the thylakoid membrane, but there is no indication that solubilization and activation are part of the normal function of the enzyme in the chloroplast.…”

mentioning

confidence: 99%

Spinach Thylakoid Polyphenol Oxidase

Golbeck

Cammarata²

1981

Plant Physiol.

144

View full text Add to dashboard Cite

Polyphenol oxidase activity (E.C. 1.14.18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. The higher molecular weight enzyme is the predominant form in freshly isolated preparations but on aging or further purification, the amount of lower molecular weight enzyme increases at the expense of the higher.Sonication releases polyphenol oxidase from the membrane largely in the latent state. C18 fatty acids, especially linolenic acid, are potent activators of the enzymic activity. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time.Purified Polyphenol oxidase (o-diphenol: 02 oxidoreductase)2 has been found in chloroplasts of nearly a dozen higher plants (2,3,9,14,16,27 were reported to be interconvertible. At present, it is uncertain whether or not the thylakoid-bound and stromal forms of the enzyme are related. The enzymic activity of plant polyphenol oxidase is latent. Activation can be achieved by treating extracts or membranes with detergents (16), acid or alkali (12), denaturing agents (22), or with proteolytic enzymes such as trypsin (27) or trypsin plus carboxypeptidase a (19). In many cases, the enzyme is activated upon release from the thylakoid membrane, but there is no indication that solubilization and activation are part of the normal function of the enzyme in the chloroplast. Indeed, the only physiological activator known is the process of aging.In this paper, we report the isolation, purification, and several properties of thylakoid-bound polyphenol oxidase from spinach chloroplasts. We demonstrate that the enzyme can be liberated from the thylakoid membrane largely in the latent state, and that activity can be initiated in the bound and released forms by a group of physiologically important molecules, the fatty acids. MATERIALS AND METHODSReagents and Chemicals. Linolenic acid was purchased from Aldrich; coumaric acid from Calbiochem; lithium dodecyl sulfate from BHD Chemicals; and trypsin from Nutritional Biochemicals Corporation. The protein standards ovalbumin, chymotrypsinogen, and ribonuclease A were supplied by Pharmacia, and human IgG was supplied by Miles Laboratories. Protein standards for SDS gel electrophoresis were obtained from Bio-Rad Laboratories. The remaining reagents and buffers were purchased from Sigma.Protein Determination and Enzyme Assays. Protein was determined according to the method of Bradford (4) using bovine plasma gamma globulin as primary standard. Chl was determined in 80o acetone (2). Polyphenol oxidase activity was assayed by measuring 02 uptake coupled to the oxidation of DL-DOPA using a Clark-type electrode. Unless otherwise stated, the el...

show abstract

“…The enzyme is ubiquitous and is found in a variety of multiple forms. Many of these forms, especially those found in broad beans, can be activated from a latent state by SDS (1,5,7,10,17). Treatment of PPO with trypsin has also been used to activate the enzyme ( 18) and to show generation of a slightly lower molecular mass form (about 43 kD) ofa purified broad bean enzyme which still retained catalytic activity (8).…”

Section: Methodsmentioning

confidence: 99%

Polypeptide Composition and Amino-Terminal Sequence of Broad Bean Polyphenoloxidase

Flurkey¹

1989

Plant Physiol.

View full text Add to dashboard Cite

Polyphenoloxidase was purified from broad bean (Vicia faba) leaves. The purified enzyme contained two immunocross-reactive proteins of approximately 60 to 65 and 43 to 45 kilodaltons. Further electrophoretic separation resolved these proteins into doublets with molecular mass of 61.5, 60, 44.5, and 43 kilodaltons, respectively. Each of the four polypeptides was transferred to Immobilon and subjected to microprotein sequencing. All the polypeptides showed the same amino acid sequence up to residue 9 but some variations occurred thereafter. The amino-terminal sequence contained a large number of proline and serine residues. These results suggest that the four polypeptides were derived from a common parent form and that a posttranslational modification(s) must have occurred to account for the difference in their apparent size.

show abstract

Latent phenolase in extracts of broad-bean (Vicia faba L.) leaves. Activation by acid and alkali

Cited by 117 publications

References 9 publications

Activation of Polyphenoloxidase in Pear Fruits by High Pressure Treatment.

Activation of Polyphenoloxidase in Pear Fruits by High Pressure Treatment.

Spinach Thylakoid Polyphenol Oxidase

Polypeptide Composition and Amino-Terminal Sequence of Broad Bean Polyphenoloxidase

Contact Info

Product

Resources

About