Metabolism of Exogenous Malonate by Coffee Leaf Tissue

When l-¹⁴C]-malonate was supplied to discs cut from matureleaves of Coffea arabica, ¹⁴CO₂ was released (approximately12% of the total CO₂ respired) and organic acids of the Krebscycle, uronic acids, sugars and amino acids became radioactive.There was no incorporation of MC into either lipids or phenoliccompounds. The formation of glucose from malonate has not beenobserved in other studies with plant tissues. The synthesisof labelled glucose together with an active pentose phosphatepathway that is stimulated by malonate explains the accumulationof radioactive phosphogluconate in the leaf discs. Tentativeproposals are made for pathways to account for the results obtained. Key words: Coffee leaves, Malonate metabolism, Pentose phosphate pathway