Fig. 6.

The effect of CRBP1 on atRA formation and CRBP expression level in the human testis. The effect of CRBP1 on atRA formation by testicular S10 protein and by recombinant ALDH1A1, ALDH1A2, and ALDH1A3 was determined and the formation of atRA from 300 nM holo-CRBP compared with free at-retinal (300 nM) is shown (A). The concentration of 300 nM was chosen to mimic expected in vivo concentrations as closely as possible. CRBP1 expression in the testis S10 fractions was quantified in all subjects by ELISA and the expression levels are shown (B). The relative contribution of each ALDH1A enzyme to atRA formation in the presence or absence of CRBP1 was predicted from a substrate (at-retinal or holo-CRBP) at 100 nM as described in the Materials and Methods and the predicted percent contribution by each ALDH1A is shown in (C).