Interaction of muscle glycolytic enzymes with thin filament proteins.

Purified glycolytic enzymes were individually chromatographed through columns of Sepharose 4B containing a covalently bound F-actin-tropomyosin complex. Five of these enzymes, aldolase, glyceraldehyde-phosphate dehydrogenase, lactate dehydrogenase, pyruvate kinase, and phosphoglycerate kinase were able to interact with the complex. Glucosephosphate isomerase, triosephosphate isomerase, phosphoglycerate phosphomutase, and enolase did not bind to the F-actin-tropomyosin matrix. One nonbinding enzyme, phosphoglycerate phosphomutase, was observed to interact with F-actin-tropomyosin if the column was preloaded with lactate dehydrogenase. Since at least four other glycolytic enzymes did not associate with actin directly, it is suggested that if a glycolytic enzyme complex exists, these nonadsorbing enzymes must interact with one or more of the enzymes which do bind to actin.

AMP photophosphorylation and binding by chloroplasts.

Stoichiometric amounts of chloroplast thylakoids photophosphorylate free AMP to tightly bound ADP. Free ADP is a poor competitor for this AMP photoreaction, which saturates below 16 micronAMP. The inhibitor, diadenosine pentaphosphate, abolishes AMP photophosphorylation, and inhibits dark ADP binding. Taken together, these data imply that this photoreaction involves the high affinity nucleotide binding site(s) of chloroplast coupling factor CF1, and that little mixing with free nucleotides occurs.

Adenosine triphosphate and diphosphoglycerate levels in red blood cells from patients with Down's syndrome.

The levels of ATP and ATP plus DPG were significantly elevated in erythrocytes from Down's syndrome patients when compared to erythrocytes from age matched controls. The hemoglobin content and hematocrit values were significantly reduced. The resultant tendency towards anemia probably explains the elevation in metabolite levels.