Highest production of xylose Isomerase by Neurospora crassa grown with
different carbon sources was at 0.014 U mg(-1) with D-xylose. The enz
yme exhibited maximum activity at pH 8.0 and 70 degrees C and retained
100% activity at 45 degrees C for 30 min at pH 8.0. It was activated
by 8 mM Mg2+ whereas 2 mM Co2+ afforded protection against inactivatio
n by heat. The K-m for xylose was 10 mM and 22 mM for xylose isomerase
and xylose reductase respectively at 28 degrees C and pH 7.0. This Is
the first report on the presence of xylose isomerase in N. crassa and
the existence of two different pathways for the utilization of D-xylo
se.