Involved in the biosynthesis of (S)-coclaurine, the common precursor of all benzylisoquinoline alkaloids such as morphine, sanguinarine, codeine or papaverine. Condenses dopamine and 4-hydroxyphenylacetaldehyde. (4-hydroxyphenyl)acetaldehyde + dopamine = (S)-norcoclaurine + H2O Activity doubles within 5 hours of elicitor treatment and continues to increase for at least 80 hours. Sigmoidal saturation kinetics suggesting positive cooperativity in the binding of dopamine. Optimum pH is between 6.5 and 7.0. Optimum temperature is 50 degrees Celsius. Alkaloid biosynthesis; (S)-reticuline biosynthesis. Detected in roots, stems, leaves, flower buds and germinating seeds. Belongs to the BetVI family. The tissue specificity and the characterization shown in PubMed:11722126 are from a soluble protein extract not making the distinction between the two proteins produced by NCS1 and NCS2.