β-(Pyrazol-1-yl)-L-alanine (β-pyrazole-L-Ala; β-PA), a model non-proteinaceous amino acid was synthesized using recombinant Escherichia coli cells that express cysteine synthase and enzymes that regenerate acetyl-CoA. In Method A, β-PA was synthesized from L-Ser and pyrazole using recombinant cells that express wild-type serine acetyltransferase (SAT), O-acetylserine sulfhydrylase-A (OASS-A), acetate kinase (AK), and phosphotransacetylase (PTA). Under the optimized condition, β-PA was produced at 140 mM from 200 mM L-Ser and 200 mM pyrazole. On the other hand, in Method B, O-acetyl-L-serine (OAS) was secreted into the broth, using the cells that express SATΔC20 (truncated SAT), OASS-A, AK, and PTA. Under optimized conditions OAS accumulated in the broth at levels of around 100 mM. The secreted OAS was efficiently converted to β-PA at levels of around 90 mM from 105 mM OAS using free OASS-A. In both Methods A and B, the addition of glucose was essential for the efficient production of β-PA and OAS, respectively.