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A feasibility study was instituted to determine if women with postmenopausal breast cancer would follow a low-fat diet (20% of kcal) for at least four months. Nineteen women, whose baseline food intake was 1,504 +/- 420 kcal with 56 +/- 16 g of fat, reported a decrease in fat intake to 21 +/- 6 g after two months of dietary intervention. Serum concentrations of cholesterol, HDL cholesterol, and estradiol were significantly reduced by the fifth month on the diet. We conclude that self-selected patients can adhere to a low-fat diet, and that serum cholesterol may serve as an indicator of dietary compliance.

The enzyme responsible for the direct phosphorylation of pyruvate during gluconeogenesis in Acetobacter xylinum has been purified 46-fold from ultrasonic extracts and freed from interfering enzyme activities. The enzyme was shown to catalyze the reversible Mge+ ion-dependent conversion of equimolar amounts of pyruvate, adenosine triphosphate (ATP), and orthophosphate (Pi) into phosphoenolpyruvate (PEP), adenosine monophosphate (AMP), and pyrophosphate (PP). The optimal pH for PEP synthesis was pH 8.2; for the reversal it was pH 6.5. The ratio between the initial rates of the reaction in the forward and reverse directions was 5.1 at pH 8.2 and 0.45 at pH 6.5. The apparent K, values of the components of the system in the forward reaction were: pyruvate, 0.2 mM; ATP, 0.4 mM; Pi, 0.8 mM; Mg2+, 2.2 mM; and for the reverse reaction: PEP, 0.1 mM; AMP, 1.6 ,uM; PP, 0.067 mM; Mg2+, 0.87 mm. PEP formation was inhibited by AMP and PP. The inhibition by AMP was competitive with regard to ATP (Ki = 0.2 mM). The reverse reaction was in-211 Vol. 104,No. 1 Printed in U.S.A.

Tomato fruit (Lycopersicum esculentum Mil) from green, pink, and red stages were assayed for changes in the activity of ribulose diphosphate carboxylase and oxygenase, phosphoenolpyruvate carboxylase, changes in the levels of glycolate and respiratory gas exchange. The ribulose diphosphate carboxylase activity decreased as the fruit ripened. By comparison, the ribulose diphosphate oxygenase activity increased during the transition from the green to the pink stage, and declined afterward. The changes in the endogenous glycolate levels and the respiratory gas exchange, as observed at different stages of ripening, resembled the changes in the ribulose diphosphate oxygenase activity. The utilization of glycolate in further metabolic activity may result in the formation of peroxidases required for the onset of ripening.

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