Regulation of Climacteric Respiration in Ripening Avocado Fruit

Abstract

Ripening of avocado fruit is associated with a dramatic increase in respiration. In vivo 31P nuclear magnetic resonance spectroscopy revealed large increases in ATP levels accompanying the increase in respiration. Both glycolytic enzymes, phosphofructokinase, and pyrophosphate: fructose-6-phosphate phosphotransferase were present in avocado fruit with the latter activity being highly stimulated by fructose 2,6-bisphosphate. Fructose 2,6-bisphosphate levels increased approximately 90% at the onset of ripening, suggesting that the respiratory increase in ripening avocado fruit may be regulated by the activation of pyrophosphate:fructose-6-phosphate phosphotransferase by an increase in fructose 2,6-bisphosphate.

Changes in Sugars, Enzymic Activities and Acid Phosphatase Isoenzyme Profiles of Bananas Ripened in Air or Stored in 2.5% O2 with and without Ethylene

“…De Leo and Sacher (9) and Sacher (33) suggested that the increased AP may be involved in the hydrolysis of mononucleotides, which may limit -the synthesis of RNA necessary for the maintenance of the levels of proteins required to sustain cell integrity. This hypothesis may not be sustainable because in most fruits the levels of ATP increase during the course of ripening (2,32,34,38). Based on the effects of inhibitors of both translation and transcription, De Leo and Sacher (9) concluded that the increase in AP activity was due to the de novo synthesis of the enzyme which was dependent upon the synthesis of RNA.…”

Role of Sucrose Phosphate Synthase in Sucrose Biosynthesis in Ripening Bananas and Its Relationship to the Respiratory Climacteric

“…201 During ripening, bananas undergo a respiratory climacteric. Mitochondria of climacteric fruit remain tightly coupled throughout ripening (4,31,37) and presumably provide the necessary ATP for the synthesis of UDP-Glc, a substrate required for sucrose synthesis.…”

Metabolically Driven Self-Restoration of Energy-Linked Functions by Avocado Mitochondria

“…There is, furthermore, an interesting analogy between the abundant phosphate esterification observed during mitochondrial self-restoration in vitro and the early findings by Young and Biale (40), recently confirmed by Bennett et al (3), that cellular ATP content increases during the climacteric rise in avocados. Whether factual or coincidental, this analogy underscores the potential role of quasi-autonomous mitochondria in meeting the energy needs of cells under stress.…”

“…Except for the small amount of ATP and two unidentified minute fractions (No. 45 and 50), the ¢ ,^ff 3 bulk of organically bound 32P in the medium appeared as a t \ \ s single peak (X) that was To amplify the temporal relationship between the flux of Pi and changes in RC, mitochondria were allowed to stress for increasing periods of time before restoration was initiated (Fig. 5, A and B).…”