Erna Meller

The biosynthesis of δ-aminolevulinic acid in greening maize leaves

Abstract In greening maize leaves δ-aminolevulinic acid (ALA) was not formed from succinyl-CoA and glycine as shown by the incorporation of [ 14 C]-labeled

Synthesis of 5-aminolevulinic acid-[14C] by cell-free preparations from greening maize leaves

Abstract The conversion of 2-ketoglutarate-[14C] to 5-aminolevulinic acid-[14C] (ALA) by a cell-free system from maize leaves is described. Optimal conversion was achieved at pH 6.2 using a 20 000 g supernatant after gel filtration through Sephadex G-25. The formation of ALA required Mg2+, an amino donor (alanine or glutamate), pyridoxal phosphate and NADH. NADPH was somewhat less effective.

Characterization of S1/mung-bean-type nuclease activity in plant cell suspensions

Abstract A nuclease activity was detected in cultured cells of various plants. The enzyme is excreted into the growth medium and degrades single-stranded forms of nucleic acids. This activity has been characterized as an S1/mung-bean-type nuclease, also by its ability to cleave supercoiled DNA only at specific sites. The growth media conditions (low pH and metal ions) favor the activity of this nuclease, while ethylenediamine tetraacetic acid (EDTA) inhibits its activity and polyethylene glycol (PEG) slows the reaction. This activity should be taken into account when transforming plant cells since RNA degrades almost immediately and plasmids are linearized when incubated with the cells. This is especially important since the effect of the topology of certain DNA regions on gene expression is well documented, and linear plasmids were found superior to supercoils for plant cell transformation.