Catalyzes the dehydration of (2R,3S)-beta-hydroxyaspartate ((3S)-3-hydroxy-D-aspartate) into iminosuccinate. Is essential for the growth of P.denitrificans in the presence of glycolate and glyoxylate since it functions in glyoxylate assimilation via the beta-hydroxyaspartate cycle (BHAC). (3S)-3-hydroxy-D-aspartate = H2O + iminosuccinate kcat is 35 sec(-1). Induced by glycolate. Abolishes growth on glycolate or glyoxylate, but the deletion mutant strain is still able to grow on acetate, succinate or glucose with comparable growth rates as for the wild type. Iminosuccinate is a labile compound that spontaneously decays into free ammonia and oxaloacetate in solution. The beta-hydroxyaspartate cycle (BHAC) consists of BhcA, BhcB, BhcC, and BhcD enzyme activities. Overall, it converts two molecules of glyoxylate (C2) into oxaloacetate (C4) without the loss of carbon as CO2, under consumption of just one reducing equivalent and regeneration of the catalytic amino donor, which makes it one of the most efficient glyoxylate assimilation pathways. This cycle is of ecological importance in the assimilation of phytoplankton-derived dissolved organic carbon in marine environments by marine Proteobacteria, and suggests a trophic interaction between autotrophic phytoplankton and heterotrophic bacterioplankton. Oxaloacetate formed in the BHAC can directly enter the tricarboxylic acid cycle or serve as substrate for anabolic reactions.