The invention relates to a method for obtaining the molybdopterin derivative precursor Z, wherein an over-production of precursor Z occurs in host organisms by recombinant expression of precursor Z synthesizing proteins. The invention further relates to the use of precursor Z for the production of a means for the therapy of human molybdenum cofactor deficiency and associated diseases, which may be directly or indirectly attributed to an altered molybdenum cofactor synthesis, whereby precursor Z is used as essential component of said therapy means.