The invention relates to norcoclaurine synthases and substrate binding sites having one or more site-specific mutation which increase the activity, when compared to the wild type synthase, of the condensation of 4-HPAA and dopamine to (S)-norcoclaurine and/or 3,4-DhPAA and dopamine to (S)-norlaudanosoline. The inventors both identified specific mutations corresponding to at position 73, 75, 77, 82, 99, 114, 141, 142, 147, 152, 174 and/or 178 in the count according to SEQ ID No: 1, and sites corresponding to the binding domains defined in SEQ ID NO: 4 and 5, where the mutated increase of the activity may be positioned within these norcoclaurine synthases. These domains are conserved regions.

The purpose of the present invention is to provide a recombinant host cell which is capable of efficiently and easily producing a benzylisoquinoline alkaloid (BIA), in particular, tetrahydropapaveroline, 3-hydroxycoclaurine, 3-hydroxy-N-methylcoclaurine and/or reticuline, and a method for efficiently and easily producing these BIAs using the host cell. The present invention pertains to a recombinant host cell for producing a benzylisoquinoline alkaloid (BIA), in particular, tetrahydropapaveroline (THP), 3-hydroxycoclaurine, 3-hydroxy-N-methylcoclaurine and/or reticuline, in which a wild-type aromatic aldehyde synthase (AAS) or a mutant thereof and a wild-type aromatic amino acid decarboxylase (AAAD) or a mutant thereof are expressed.

The invention relate to genetically modified hosts cell comprising a pathway having enhanced production of one or more benzylisoquinoline alkaloids wherein the cell expresses heterologous insect genes encoding insect demethylases converting thebaine into northebaine, thebaine into oripavine, thebaine into nororipavine and/or oripavine into nororipavine.

Methods and engineered cells are provided for increasing activity of a norcoclaurine synthase in a microbial cell. The method comprises, within the engineered microbial cell, contacting an engineered norcoclaurine synthase with a substrate, wherein contacting the substrate with the engineered norcoclaurine synthase increases conversion, within the engineered microbial cell, in comparison to a non-engineered norcoclaurine synthase.

The invention relates to norcoclaurine synthases and substrate binding sites having one or more site-specific mutation which increase the activity, when compared to the wild type synthase, of the condensation of 4-HPAA and dopamine to (S)-norcoclaurine and/or 3,4-DhPAA and dopamine to (S)-norlaudanosoline. The inventors both identified specific mutations corresponding to at position 73, 75, 77, 82, 99, 114, 141, 142, 147, 152, 174 and/or 178 in the count according to SEQ ID No: 1, and sites corresponding to the binding domains defined in SEQ ID NO: 4 and 5, where the mutated increase of the activity may be positioned within these norcoclaurine synthases. These domains are conserved regions.

The invention relates to norcoclaurine synthases and substrate binding sites having one or more site-specific mutation which increase the activity, when compared to the wild type synthase, of the condensation of 4-HPAA and dopamine to (S)-norcoclaurine and/or 3,4-DhPAA and dopamine to (S)-norlaudanosoline. The inventors both identified specific mutations corresponding to at position 73, 75, 77, 82, 99, 114, 141, 142, 147, 152, 174 and/or 178 in the count according to SEQ ID No: 1, and sites corresponding to the binding domains defined in SEQ IN NO: 4 and 5, where the mutated increase of the activity may be positioned within these norcoclaurine synthases. These domains are conserved regions.