NADP-dependent oxidoreductase; part of the lnb gene cluster that mediates the biosynthesis of diastereomeric piperazines. Lna and lnb clusters encode sets of enzymes that produce overlapping sets of previously undescribed metabolites such as piperazinomycin-like metabolites or morpholine (PubMed:23281040). The lna and lnb biosynthetic pathways appear to be part of a signaling network that controls the formation of sclerotia, a resilient overwintering structure (PubMed:23281040). One primary function of the non-canonical nonribosomal peptide synthetases lnaA and lnbA consists in the reduction of L-tyrosine (PubMed:23281040). The presence in the clusters of tailoring enzymes such as the oxidoreductases lnaB, lnbB, lnaE or lnbE, as well as of the cytochrome P450 monooxygenases lnaC, lnaD, or lnbC, might explain formation of various diastereomeric piperazines (PubMed:23281040). Secondary metabolite biosynthesis. Belongs to the NADP-dependent oxidoreductase L4BD family.