Tyrosine aminotransferase was highly purified from rat livers in which the enzyme had been induced by a glucocorticoid hormone. The preparation eluted from a DEAEcellulose column as a single peak gave a single precipitin line by the Ouchterlony double diffusion precipitin reaction and sedimented as a single boundary in the ultracentrifuge with an s20,W of 5.9. A molecular weight of 91,000 was d...

Salt stress is a major environmental factor influencing plant growth and development. To identify salt tolerance determinants, a genetic screen for salt overly sensitive (sos) mutants was performed in Arabidopsis. We present here the characterization of sos4 mutants and the positional cloning of the SOS4 gene. sos4 mutant plants are hypersensitive to Na(+), K(+), and Li(+) ions. Under NaCl stre...

Chemical modification studies with pyridoxal 5'-phosphate have indicated that lysine(s) appear to be at or near the active site of Escherichia coli glutamine synthetase (Colanduoni, J., and Villafranca, J. J. (1985) J. Biol. Chem. 260, 15042-15050; Whitley, E. J., Jr., and Ginsburg, A. (1978) J. Biol. Chem. 253, 7017-7025). Enzyme samples were prepared that contained approximately 1, approximat...

Many compounds have been described that inhibit growth by interfering at one point or another in the metabolism of vitamin Bg (2). These include a variety of compounds related structurally to the vitamin, together with an array of carbonyl reagents generally known to inhibit pyridoxal phosphate enzymes. In no case has the site of action of such inhibitors in tivo been established. One of the fi...

The biologically active form of vitamin B6, pyridoxal 5'-phosphate (PLP), is a cofactor in over 160 enzyme activities involved in a number of metabolic pathways, including neurotransmitter synthesis and degradation. In humans, PLP is recycled from food and from degraded PLP-dependent enzymes in a salvage pathway requiring the action of pyridoxal kinase, pyridoxine 5'-phosphate oxidase and phosp...

Isonicotinic acid hydrazide (isoniazid) causes a large increase in the salt-solubility of collagen when injected into chick embryos; this change is accompanied by the inactivation of lysyl oxidase (EC 1.4.3.13), the enzyme responsible for initiating cross-link formation in collagen and elastin. In addition, isoniazid markedly decreases the liver content of pyridoxal phosphate. The depletion of ...

NaBH4-reduced phosphorylase b is a catalytically active species which retains many of the properties of the native enzyme. One property that is strikingly different, however, is the spectral behavior of bound pyridoxal phosphate. At pH 7.0, the pyridoxal phosphate shows essentially no absorption at 333 nm, where pyridoxal phsophate in the native enzyme absorbs; absorption at 333 mn returns upon...