Inhibition of the vitamin B12 binding capacity of proteins by the hydrolysis product of cyclophosphamide.

The inhibitory effect of cyclophosphamide hydrolysis product (CPHP) on vitamin B12 binding ability to proteins has been established. The ester N-(2-chloroethyl)-N'-(3-phosphopropyl)-ethylenediamine hydrochloride is probably responsible, in vitro, for blocking the protein binding sites. Preincubation of proteins with vitamin B12 prevents the inhibitory effect of CPHP.