The amino acid composition and some properties of the NAD + -specific glutamate dehydrogenase from Neurospora crassa

The red algal-higher fungi phylogenetic link: the last ten years

The review of the red algal theory for ancestry of Ascomycetes and Basidiomycetes published 10 years ago by the author is updated. Criticisms are answered and new data are discussed. The production of choline sulfate, lenthionine and lanosol are added to the biochemical similarities between red algae and higher fungi. Distribution of polyols is shown to be in favour of the origin of higher fungi from parasitic red algae. As predicted, NADP-linked glutamate dehydrogenase has been found in red algae, and additional reports of chitin in various algae have been published. New supporting data come from the ultrastructure of red algae: mitosis outside the Ceramiales and ultrastructure of vegetative cells and tetrasporocysts of Corallinaceae. On the other hand, the discovery of proplastids in Holmsella makes it less fungus-like. However, no decisive argument has yet been produced for or against the theory. Further light should be expected from protein and nucleic acid sequences. Promising partial sequences of cytochrome c have indeed been published for red algae but the published 5 S ribosomal RNA sequences have not proven relevant to the problem. Sequences of the slower-evolving large rRNA and cytochrome c of red algae could provide convincing evidence and are urgently needed.

Purification and properties of glutamate dehydrogenase from Vigna unguiculata (L.) walp

Glutamate dehydrogenase (L-glutamate: NAD(+) oxidoreductase (deaminating), EC 1.4.1.2) from 2-day-old seedlings of Vigna unguiculata was purified more than 500-fold. The enzyme gave one diffuse protein band on polyacrylamide gel electrophoresis and its subunit molecular weight was 51,000±5% as determined by sodium-dodecyl-sulfate-gel electrophoresis. The enzyme was active with NADH, NAD(+) and NADPH in the ratio of 126:1:2 with pH optima of 8.0, 10.0 and 6.0 respectively. Inhibition of enzyme by EDTA was reversed by Ca(2+) and Mn(2+) while reduced glutathione reversed inhibition by p-hydroxymercuribenzoate. The enzyme was highly specific for L-glutamate and α-ketoglutarate showing very little or no activity with a range of other amino acids and keto acids. Values for Michaelis constants were: NAD(+), 0.285 mM; NADH, 0.059 mM; α-keto-glutarate, 1.79 mM; ammonium sulphate, 28.6 mM; L-glutamate, 16.7 mM.