Pathwaysin Normaland LeukemicLeukocytes

drogenase (decarboxylating) were less active in leukocytes (mostly myeloblasts) from eight patients vith acute myeloblastic leukemia (I) than in leukocytes (mostly granulocytes) from 16 normal subjects (II) or 16 patients with chronic myelocytic leukemia (Ill). (b) Of the enzymes of the citrate cleavage pathway, ATP citrate lyase and malate dehydrogenase (decarboxylating) (NADP) were virtually absent in the cells studied. (c) lsocitrate dehydrogenase (NADP+), aspartate aminotransferase, and alanine aminotransferase, which, together with the much more active malate dehydrogenase, constitute a newly proposed NADPH-forming metabolic cycle, showed a higher activity in I than in II or Ill, and therefore could compensate, as concerns NADPHgeneration, for the low activity of pentose cycle dehydrogenases. We are not sure whether the enzymatic characteristic of I cells is attributable to their immaturity or to their leukemic nature. AddItIonal Keyphrases: pentose phosphate pathway NADPH-formingcycle