Also oxidizes L-histidinel.

The Neurospora enzyme also catalyses the reaction of EC 3.5.4.19 (Phosphoribosyl-AMP cyclohydrolase) and EC 3.6.1.31 (Phosphoribosyl-ATP pyrophosphatase).

This enzyme catalyzes the terminal step in the biosynthesis of histidine in bacteria, fungi, and plants, the four- electron oxidation of L-histidinol to histidine.

In bacteria HDH is a single chain polypeptide; in fungi it is the C-terminal domain of a multifunctional enzyme which catalyzes three different steps of histidine biosynthesis; and in plants it is expressed as nuclear encoded protein precursor which is exported to the chloroplast.

As a signature pattern it's been used a highly conserved region located in the central part of HDH. This region does not correspond to the part of the enzyme that, in most, but not all HDH sequences contains a cysteine residue which, in Salmonella typhimurium, has been said to be important for the catalytic activity of the enzyme.
Reference