Effects of environmental anoxia on concentrations of free amino acids and kinetic properties of glutamate dehydrogenase in three body parts of Phascolosoma arcuatum (Sipuncula)

Abstract

The body wall (BW), introvert cum retractor muscles (ICRM) and digestive tract (DT) of the sipunculid worm Phascolosoma arcuatum had different biochemical adaptations to anoxia with reference to amino acid metabolism. Although aspartate degradation occurred in all three body parts of the anoxic worm, alanine and glutamate accumulated only in the ICRM and DT, and not the BW. Hence, in the BW, the amino group of aspartate was not transferred to alanine during anoxia, but was possibly released as ammonia through glutamate. The kinetic properties of glutamate dehydrogenase (GDH) from the BW and ICRM were altered during anoxia to enhance the glutamate deaminating activity. Although alanine and glutamate were accumulated in the ICRM of the anoxic P. arcuatum, the decrease in aspartate content was unable to account for the increase. Results indicate that it was in the DT of the anoxic worm that glutamate was likely to act as an intermediate to shuttle the amino group between aspartate and alanine. The kinetic properties of the GDH from this body part of P. arcuatum were unaltered by anoxia. © 1993.