A starch-hydrolyzing enzyme present in extracts of the cotyledons of germinating peas has been purified over 34oo-fold. Several independent criteria show that this activity is due to an amylase of the a-type (a-I,4-glucan-4-glucanohydrolase, EC 3.2.1.1). The enzyme exhibits maximal activity in the pH range 5-3-5-9; the Michaelis constant (Krn) and energy of activation (Ea) for ~he enzyme-catalyzed reaction are 2" I'O -4 g soluble starch per ml and 7600 cal/mole, respectively. Calcium ions protect the amylase against heat inactivation, whereas incubation of the enzyme with 5" lO-3 M EDTA for 20 rain at room temperature results in complete loss of activity. With amylose and amylopectin as substrates, this enzyme is similar in action pattern to other known plant a-amylases.

Amylase activity is present in extracts of the axis tissue of etiolated pea seedlings. Several lines of evidence establish that this starch-hydrolyzing activity is due to the presence of a fl-amylase (a-I,4-glucan maltohydrolase, EC 3.2.1.2); the properties of this enzyme are reported. Maltase (EC 3.2.1.2o) activity is also present in extracts of the same tissues. Since a-amylase (EC 3.2.1.1) activity appears in the germinating cotyledon, the following hydrolytic pathway for the degradation of starch to glucose is present in the pea seedling: a-amylase soluble fl-amylase a-glucosidase starch > oligosaccharides > maltose > glucose The importance of this pathway is considered in relation to the alternative route for starch catabolism, namely, the phosphorolytic pathway involving the enzyme phosphorylase (EC 2.4.1.1).

Cephaloglycin, cephalothin, cephaloridine, cefoxitin, and cephacetrile are cephalosporin antibiotics that react with alkaline picrate solution to give a creatinine-like response. The mechanism of this reaction is not known, and several structurally similar compounds do not react under these same conditions. Because large quantities of a cephalosporin antibiotic may be administered to a patient with limited ability to excrete the drug (as occurs with compromised renal function), the magnitude of this interference can be appreciable. It does not appear possible to avoid the cephalosporin-caused interference by the use of "kinetic" creatinine methods.

Ischemic renal failure was produced in rabbits by occluding the renal arteries for 90 min. Group 1 (n = 8) received radiocontrast media at the time of occlusion, group 2 (n = 8) 24 h after occlusion, and group 3 (n = 8) 3 days after occlusion. Group 4 (n = 12) was subjected to ischemic injury alone, group 5 (n =4) served as sham-operated controls and group 6 (n = 4) did not undergo surgery but received radiocontrast media. Serum creatinine concentration in group 1 increased to a greater degree (p < 0.001) than all other groups and did not return to normal during the 8-day observation period. Creatinine concentration in groups 2, 3, 4, and 6 were comparable and significantly increased compared to sham-operated group (p < 0.05). Urinary excretion of alanine aïninopeptidase and N-acetyl-β-glucosaminidase in group 1 was significantly greater than all other groups (p < 0.05). Microscopic analysis indicated tubular necrosis was more prominent in group 1. Radiocontrast media is nephrotoxic and in the setting of ischemic injury may prevent recovery of renal function. Toxicity was dependent on the time of administration since functional impairment was not increased if dye was given 1 or 3 days after ischemic injury.

Homocitrullylamino adenosine inhibits the incorporation of Ii4Clamino acids into a hot acid-insoluble form in cell-free systems derived from Escherichia coli and rat liver.The concentration necessary for one-half maximal inhibition in the E. coli system is i.l. Io -4 M. Addition of the intact molecule is necessary for the maximum inhibition. The inhibition does not appear to involve the activation of the amino acids or their transfer to s-RNA, but rather exerts its effect, like puromycin, at the level involving the s-RNA ribosomal complex.