Synthesis and antibacterial activity of new C-10 quinolonyl-cephem esters.

A series of cephalosporins derived from cephalothin containing an ester-linked quinolonyl substituent at the C-10 position (C-10 quinolonyl-cephem esters) has been prepared and evaluated for in vitro antibacterial activity. The C-10 quinolonyl-cephem esters exhibited a broadened spectrum of activity when compared with cephalothin and the corresponding quinolones, including activity against beta-lactamase-producing bacteria.

Studies on the specificity of phosphorylase kinase using peptide substrates.

The action of phosphorylase kinase on synthetic peptides is reported. These peptides are variants of the amino acid sequence. Ser-Asp-Gln-Glu-Lys-Arg-Lys-Gln-Ile-Ser-Val-Arg-Gly-Leu, found in the natural substrate, phosphorylase b.

Pyridoxal phosphate-dependent conformational states of glycogen phosphorylase as probed by interconverting enzymes.

The interaction between pyridoxal 5'-phosphate and the convertible serine of glycogen phosphorylase has been investigated by using: specific interconverting enzymes, phosphorylase kinase and phosphorylase phosphatase; effectors, glucose and glucose 6-phosphate; and a protein kinase and trypsin. Both phosphorylase kinase and phosphorylase phosphatase utilized the native protein while having little influence on the apoprotein. Removal of a peptide containing the critical serine residue gave phosphorylase b' from which the pyridoxal 5'-phosphate in phosphorylase has an important effect on enzymic interconversion.