Kinetic studies of the lipid requirement of mitochondrial cytochromec oxidase

The lipid requirement of cytochromec oxidase was reinvestigated using both acetone and phospholipase A to deplete mitochondria of lipid. Removal of lipid resulted in a decrease in both the apparentK _m for cytochromec and apparentV _max when compared to control mitochondria. Addition of phospholipid to the assay mixture reactivated the enzyme. For both treatments theK _m returned to the control value. With phospholipase A treated mitochondria theV _max increased to near the control value, while acetone extracted mitochondria could be restored to aV _max of 1/2 that of the control. Detergent does not substitute for phospholipid and inhibits the reactivation with phospholipid.This research was supported in part by United States Public Health Service Research Grant AM-14632 and a Grant-in-Aid of the American Heart Association.     

Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.