Polyphenol oxidase inhibitors

Sondey S.M., Seib P.A., El-Atawy Y.S. Control of enzymatic browning in apple with ascorbic acid derivatives, polyphenol oxidase inhibitors, and complexing agents. Journal of Food Science, 53 997-1002 (1989). 

Effects of a Polyphenol Oxidase Inhibitor on Extracellular Polyphenol Oxidase Activity on Mycelial Dry Weight... 

Effects of Polyphenol Oxidase Inhibitor (Piethylthiocarbamate) on Both Mycelial Dry Weight and Extracellular Polyphenol Oxidase... 

Tricand de la Goutte, J Khan, JA Vulfson, EN. Identification of novel polyphenol oxidase inhibitors by enzymatic one-pot synthesis and deconvolution of combinatorial Mhidiiies. Biotechnology and Bioengineering, 2001 75, 93-99. 

Serine Proteinase Inhibitor I Serine Proteinase Inhibitor II Cysteine Proteinase Inhibitor Aspartic Proteinase Inhibitor Polyphenol Oxidase... 

We will discuss selected current knowledge on the use of plant enzymes as bases of insect resistance the review is not comprehensive. Particular attention will be given to induced de novo synthesis of proteinase inhibitors in the tomato plant Lvcop-ersicon esculentum, and on the simultaneous use of plant polyphenol oxidases as a means of conferring resistance to insect pests. 

Extrapolation of these results to the real world suggests that the simultaneous use of PPO/phenolics and proteinase inhibitors as bases of resistance against certain insects may be mutually incompatible. If one were to rely on proteinase inhibitors as a basis, the elimination of high levels of polyphenol oxidase in the plant would not guarantee antibiotic activity because high levels of dietary protein can abolish PI toxicity (89) Hence, the activity of PI, PPO and phenolics in situ may require the manipulation of multiple plant factors. 

Table V. The Effect of Tomato Plant Foliar Polyphenol Oxidase Activity on Proteinase Inhibitors in Snodoptera exigua...

Table II gives the results of residual trypsin inhibitor levels for the various soymilk preparations. The 90 and 120 sec microwave treatments were the most effective in inactivating the trypsin inhibitor complex while hot water treated and unheated samples showed the highest levels. It is not surprising to find that microwave processing is more efficient than hot water in suppressing trypsin inhibitor considering the rapid penetration of food material by microwaves and the susceptibility of protein action to small heat induced changes in tertiary structure. Hence, Collins and McCarty (12) found microwaves produced a more rapid destruction of endogenous potato enzymes (polyphenol oxidase and peroxidase) than hot water heating.

Keywords Tyrosinase inhibitors Agaricus bisporus - Polyphenol oxidase Hyperpigmentation Vitiligo Melanogenesis - Alkaloid... 

Henderson HM, Eskin NAM, Pinsky C, et al. 1992. Pyridine and other coal tar constituents as inhibitors of potato polyphenol oxidase A non-animal model for neurochemical studies. Life Sci 51 207-210. 

Research projects in basic enzymology of polyphenol oxidase and the chemistry of non-enzymatic browning may lead to new browning inhibitors. Reviews on polyphenols oxidase (13) and on Maillard reactions (14) are available. The interest in enzymatic browning is aided by skin cancer research as melanins are the pigments involved in the coloring of human skin. 

Study of naturally-occurring enzyme inhibitors is of importance for several reasons. These include (a) the physiological importance of an inhibitor in biological material, (b) the nutritional importance of an inhibitor when the material is consumed as a food or feed, (c) the use of inhibitors to control enzymatic action, such as that of polyphenol oxidase, (d) the use of inhibitors for analysis and for purification purposes and (e) a better understanding of specific interactions among complex molecules such as proteins (examples include antigen-antibody reactions, subunit interactions in proteins, enzymatic actions). 

Further validation of the mechanism proposed for the catecholase activity of the dicopper complexes [Cu2(L66)]" , [Cu2(L55)], and [Cu2(EBA)]" " (Scheme 17) has been obtained investigating the inhibitory effect of kojic acid [5-hydroxy-2-(hydroxymethyl)-y-pyrone] (154). This fungal metabolite is one of the most efficient inhibitors of mushroom tyrosinase and other polyphenol oxidases (160,161). When the catalytic oxidation of DTBCH2 was studied in the presence of kojic acid, strong competitive inhibition was observed in the steps exhibiting substrate concentration dependence,... 

One way to prevent polymerization of the o-quinone is to remove it from the reaction mixture by chemical reduction (e.g., by ascorbate), which leads to catechols. Ascorbate, however, like many other reductants can act as an inhibitor of polyphenol oxidase. To circumvent the inhibition, the concentration of the reducing agent should be kept at a minimum. Furthermore, a borate buffer... 

---