A METABOLIC PATHWAY OF ISOCITRIC ACID IN COTYLEDONS OF A BEAN, VIGNA SESQUIPEDALIS

1. It has been established that the absence of isocitric dehydrogenaseactivity in cotyledons of Vigna sesquipedalisin the germinationstage is due to the lack of endogenous TPN. It is unlikely thatthe TCA cycle in the cotyledon is operative.
2. The activitiesof enzymes of the glyoxylate cycle, a modifiedTCA cycle, weremeasured through the germination stage. Theiractivities wereconsiderably higher in the cotyledon tissuethan in the hypocotyl.A dominant metabolic pathway of isocitricacid in the cotyledonmay be the glyoxylate cycle.
3. DPN kinase which produces TPNfrom DPN, ATP and Mg⁺⁺ was localizedin the supernatant portionof cell components in the cotyledon.Its activity was low. DPNkinase serves as a control factorfor the cotyledon metabolism.

(Received April 17, 1961; )