LIPOXYGENASE ACTIVITY IN PRICKLY PEAR FRUIT (OPUNTIA FICUS INDICA[L.] MILL. CACTACEAE)

Abstract

Prickly pear LOX activity was detected in the membrane fractions of the fruit extracts at various stages of ripening. LOX specific activity was very low in the fruit of wild plants at the green stage (0.49 ± 0.04) and increased with fruit ripening, more than doubling in the ripened fruit (1.22 ± 0.06). Moreover, it was not influenced by the cultivar, whereas it was considerably increased (13.3 ± 1.4) by agronomic processes to which prickly pear plants are submitted to improve the organoleptic properties of fruits. The apparent molecular mass of the enzyme was estimated to be 96 kDa. The enzyme had an optimum pH value of 5.5 and a clear specificity for linolenic acid, which was oxidized at a rate one and a half times that of linoleic acid, under the same reaction conditions. The involvement of prickly pear LOX in the flavor biosynthesis of the fruit is supposed. PRACTICAL APPLICATIONS Over the last decade in particular, prickly pear fruits have been widely used as food, not only the whole fruit but also processed to make juices, jams and liquors popular the world over. Prickly pear production has therefore risen considerably and consequently both the labor force employed and revenues generated have increased. For those engaged in this sector it is therefore a prime objective to maximise the profile and thereby profitability of the fruit. It is here that our research into lipoxygenase activity can play a part, as it is known that this enzyme is responsible for the organoleptic properties of fruits and vegetables. The results are presented below. The relationship between lipoxygenase specific activity and specific agronomic processes utilized to improve the fruit quality is also addressed.

Lipoxygenase activity associated to fruit ripening and senescence in chayote (Sechium eduleJacq. Sw. cv. “virens levis”)

“…97 kDa protein for TomloxB gene in tomato; Lv et al () have predicted a protein molecular weight of 103 kDa for DkLox1 gene in persimmon fruit; Schiller et al () reveled proteins with a molecular mass of about 101–105 kDa in apple fruit. Likewise, in non‐climacteric fruit Palmieri et al () calculated a molecular mass of 98 kDa for olive LOX; De Gregorio, Arena, and Giuffrida () reported an apparent molecular mass of 96 kDa in prickly pear fruit; and Leone et al () showed two groups of approximately 100 and 98 kDa for strawberry fruit.…”

“…Despite the abundant information about the LOX isoforms in most plants, to the best of our knowledge, there are no reports available on chayote LOX isoforms or their activity. These may vary in relation to substrate preference, kinetic parameters, and the positional specificity of substrate oxygenation; additionally, LOX pathway are also involved in plant morphogenesis and senescence, fruit development, as well as plant response to stress and wounding (De Gregorio et al, ).…”

Identificación de compuestos aromáticos de diferentes variedades de nopal verdura y su respuesta a la atmósfera modificada como método de conservación

“…Probablemente la falta de luz durante el almacenamiento contribuyó a la desaparición de este volátil. Se ha reportado que el 2-nonenol se origina del ácido 9-hidroperoxi-linoleico y contribuye al 30% del olor en tuna (De Gregorio et al, 2010).…”