Abstract: Lysine decarboxylase is a key enzyme involved in the upstream biosynthesis of lycopodium alkaloids (LAs) such as huperzine A, contributing to the decarboxylation of lysine to 1, 5-pentanediamine (cadaverine). Three lysine decarboxylase genes (HsLDC-L1, HsLDC-L2, HsLDC-L3) were successfully cloned from Huperzia serrata using transcriptomic sequence data mining strategy combined with reverse transcription PCR. The physicochemical properties, secondary and tertiary structures, amino acid identities, and evolutionary relationship of the three LDCs were analyzed by online bioinformatics analysis platforms and DNAMAN, MEGA 7.0 software, revealing that all of these proteins had the conserved PLP binding domain and active site residues were completely conserved in LDCs. Phylogenetic analysis showed that these LDCs were located in the same branch as other known LDCs from LA-producing plants. Accordingly, the ORFs of these three HsLDCs were inserted into different expression plasmids for further expression in E. coli. However, only HsLDC-L1 was successfully expressed in E. coli BL21 (DE3) by inserting into a pCold TF vector. The recombinant protein was purified by Ni²⁺ affinity chromatography purification. HsLDC-L1 contains 469 amino acid residues, with a calculated molecular weight of 50.50 kDa. HsLDC-L1 expectedly catalyzed the decarboxylation of lysine to produce cadaverine. In addition, HsLDC-L1 can also catalyze the generation of putrescine from ornithine. However, it cannot catalyze the decarboxylation of tyrosine, phenylalanine, tryptophan and histidine. The results not only provide insight into the biosynthesis of LAs including huperzine A, but also provide a critical genetic element for the overproduction of Δ¹-piperideine and pelletierine, the essential biosynthetic precursors of LAs, using synthetic biology strategies.