Glucose 6-phosphate, fructose 6-phosphate, fructose 1, 6-diphosphate, and triose phosphates, and the enzymes phosphofructokinase, aldolase, and glucose 6-phosphate dehydrogenase were extracted from banana fruit (Musa cavendishii, Lambert var. Valery) at the (a) preclimacteric, (b) climacteric rise, (c) climacteric peak, and (d) postclimacteric stages of ripening. The level of fructose 1 ,6-diphosphate increased 20-fold whereas the concentration of other intermediates changed no more than 2.5-fold between stages a and c. For these same extracts, phosphofructokinase activity increased 2.5-fold whereas the activity of glucose 6-phosphate dehydrogenase and aldolase changed only fractionally. (24). Young (unpublished data) measured an increase in 3P incorporation into fructose-1,6-diP during the climacteric in avocado, and an increase in fructose-1 ,6-diP was also reported in tomato (6). These observations could be explained by the activation of PFK.It was the purpose of this investigation to determine Valery were obtained from Central America via ship transport 11 to 14 days after picking. They were always dark green in color and preclimacteric. The respiration of individual fruits was monitored with an infrared gas analyzer in a continuous flow system. Humidified air was passed over the fruit at 100 ml/min at 22 C. Ripening was initiated by introducing ethylene into the air stream to give a final concentration of 1 ml/ 1. Fruits were taken for analysis in the preclimacteric stage, at early climacteric rise, at climacteric peak, and at two days postclimacteric stage. The pulp was grated into liquid nitrogen and lyophylized. The dry pulp was ground to a fine powder in a mortar and stored at -12 C.Extraction. The powders were suspended in buffered medium modified from that used by Black and Wedding (5). It consisted of 50 mm Tricine buffer, pH 8.5, 5 mm diethyldithiocarbamate, 5 mm dithiothreitol, 50 mM magnesium acetate, and 0.2% Triton X-100. This medium was used both for determining the glycolytic intermediate levels and for obtaining the crude enzyme preparation.Assay of Intermediates. The levels of glycolytic intermediates were determined by the spectrophotometric method of Fawaz and Fawaz (14). Duplicate 1 g samples from each of the four stages were weighed and homogenized in a mortar with pestle in 10 ml of the extraction medium at 2 C. The medium was added in 2.5 ml increments, and the homogenate was evenly dispersed after each increment.The crude homogenate was directly centrifuged at 105,000g (35,000 rpm) at 0 C for 20 min, and the supernatant fluids were stored in an ice bath. The precipitates were resuspended in 2.5 ml of the extraction medium and recentrifuged at 105,OOOg for 15 min. The supernatant fluids were then combined and two 4-ml aliquots were mixed with 0.4 ml of 6.6 N HCIO,. The samples were then centrifuged at 30,000g for 20 min at 0 C. The precipitates were resuspended in 2 ml of 0.6 N HC1O4, recentrifuged at 30,000g for 15 min, and the supernatant fluids were combined with those from...