Albizziin is amino acid analog which acts as a competitive inhibitor of asparagine synthetase with respect to glutamine. Albizziin has been used to isolate mutants of Chinese hamster ovary cells with alterations in levels of the target enzyme. Several classes of mutations can be distinguished on the basis of cross-resistance to beta-aspartyl hydroxamate, another amino acid analog. Studies on asparagine synthetase indicate that resistance to albizziin may be due to altered regulation of asparagine synthetase, structural mutations of the enzyme, and gene amplification.