Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. VI. Controlled Oxidations and Coupled Phosphorylations

Wiskich, Joseph T.; Young, Roy E.; Biale, J. B.

doi:10.1104/pp.39.3.312

Cited by 54 publications

(33 citation statements)

References 27 publications

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“…Mitochondria which show respiratory control by ADP when oxidizing suiccillate, malate and(I a-ketoglutarate have thuls 1 Preliminiary reports of this w%ork have appeared (10,16) (11,12,15,24). The opportunity opened uip of followilg the variations in the oxi(lative abilities of the mitochonldria (lurinlg the overall ripening process.…”

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Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. IX. The Oxidation of Pyruvate and Malate during the Climacteric Cycle

Lance¹,

Hobson²,

Young³

et al. 1967

Plant Physiol.

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Suwnmary. Mitochondria isolated from preclimacteric avocado frtuit oxidize pyrulvate at a mulch lower rate than those separated from climacteric fruit. The external addition cf thiamiine pyrophosphate (TPP) increased the rate of pyruivate oxidiation in both cases.The sttudy of the infltuence of TPP on the rate of oxidation of malate by mitochondria obtained from both preclimacteric and climacteric fruiit indicated that the effect of this cofactor coulld be uinderstood by assulming that malate was converted to pyruivate. TPP (11,12,15,24). The opportunity opened uip of followilg the variations in the oxi(lative abilities of the mitochonldria (lurinlg the overall ripening process. In the course of this stuylv it was found that the ratc of oxidation of malate was highly depencdent on the stage of the climacteric of the fruiit from which the mitochondria had been extracted. Moreover, the addition of thiamine pyrophosphate (TPP) to preclimacteric fruit particles in the presence of malate resulted in a considerable enhancement of the rate of oxidation of this substrate. At this stage of maturation the metabolism of a-ketoglutarate was also highly sensitive to the external addition of TPP (15), a situation which was not observed when the mitochondria were prepared from fruits reaching the climacteric condition,

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“…TPP (11,12,15,24). The opportunity opened uip of followilg the variations in the oxi(lative abilities of the mitochonldria (lurinlg the overall ripening process.…”

mentioning

confidence: 99%

Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. IX. The Oxidation of Pyruvate and Malate during the Climacteric Cycle

Lance¹,

Hobson²,

Young³

et al. 1967

Plant Physiol.

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“…The substances have therefore been called dwvarfing agents or growth retardants. Their overall effect is the opposite of the growth effects produced by the gibberellins, and when a retardant and a gibberellin are applied together, the retardant effects may be overcome, resulting, at least in some cases, in normal growth (6,16,20). Some authors have therefore called the retardants antigibberellins, although…”

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“…The properties of mitochondria from ripening fruits have been studied by several workers in an effort to account for the climacteric rise in respiration (8,15,20). The climacteric rise in apple and avocado fruits does not seem to be accompanied by uncoupling of oxidative phosphorylation or the loss of respiratory control (8,20).…”

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“…The climacteric rise in apple and avocado fruits does not seem to be accompanied by uncoupling of oxidative phosphorylation or the loss of respiratory control (8,20). Mitochondria from climnacteric avocados oxidize a-ketogluta-rate, pyruvate, and malate less rapidly than mitochondria from preclimacteric fruits, but the rate of succinate oxidation remains about the same (15 Heavy an(l light mitochondrial fractions were obtaine(l by first centrifuging the strained honmogenates at 4,600 X g for 5 minutes.…”

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Comparison of Mitochondria from Tomato Fruits at Various Stages of Ripeness

Dickinson¹,

Hanson²

1965

Plant Physiol.

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Isolierung und Eigenschaften von Mitochondrien aus Bl�ttern von Spinacia oleracea und Beta vulgaris

Gronebaum-Turck

Willenbrink

1971

Planta

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From mature green leaves of Spinacia oleracea and Beta vulgaris a fraction has been obtained which is enriched in mitochondria. Washed leaves were crushed in a meat-mill in an isotonic or slightly hypertonic medium containing sucrose, EDTA, MgSO4, bovine serum albumin, mercaptoethanol, KH2PO4, and HEPES as a buffer substance. After squeezing through nylon the suspension was centrifuged first at 1500xg, and following removal of the sediment a second time at 25000xg. After resuspension in a washing medium, the pellet was centrifuged in a swing-out rotor for 30 min at 35000xg on a density gradient generated from a silica sol ("Ludox HS 40"). A temperature of 2°C was maintained during the whole procedure.Whereas the usual isolation techniques are unsatisfactory for the preparation of intact leaf cell mitochondria, the above procedure enabled us to obtain a fraction from the gradient which had the following properties. The respiration rate was 29.5 μatoms O/mg protein-N/h with α-ketoglutarate as a substrate. Phosphorylation rates as calculated from the phosphate measurements and P/O ratios were low. This has been interpreted as a consequence of ATPase activity in the fraction. In polarographic studies ADP/O ratios of 1.32-2.15 with succinate as a substrate were measured. Respiratory control was also observed. This indicates the presence of tightly coupled mitochondria in the fraction.The fine structure of the mitochondria was shown to be intact as far as electron microscopical evidence can be used as a criterion. The procedure appears to be suitable for isolating active mitochondria and intact chloroplasts from green leaves. It may permit the study of interrelationships between these organelles.

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Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. VI. Controlled Oxidations and Coupled Phosphorylations

Cited by 54 publications

References 27 publications

Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. IX. The Oxidation of Pyruvate and Malate during the Climacteric Cycle

Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. IX. The Oxidation of Pyruvate and Malate during the Climacteric Cycle

Comparison of Mitochondria from Tomato Fruits at Various Stages of Ripeness

Isolierung und Eigenschaften von Mitochondrien aus Bl�ttern von Spinacia oleracea und Beta vulgaris

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