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

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.     

Cloning and characterization of a dextranase gene (dexS) from Streptococcus suis

A gene (dexS) coding for a Streptococcus suis capsular type 2 dextranase (DexS) was detected in a recombinant gene library constructed in phage λZapII, and its nucleotide sequence was determined. Sequence comparison showed that the dexS gene product had significant similarities with enzymes which hydrolyze glucose polymers. Moreover, conserved amino acids that are suggested to be part of the active site of the glucosidases are also found in DexS. The dexS gene, adjacent to the gene encoding a S. suis IgG-binding protein, encoded a protein of approximately 62 kDa which exhibited DexS activity.