Characterization of 5α-Reductase in Cultured Human Dermal Papilla Cells from Beard and Occipital Scalp Hair

In order to gain a deeper insight into the role of 5α-reductase in the growth of beards in men, we studied some kinetic properties of the enzyme in cell homogenates of cultured human dermal papila cells from beard and occipital scalp hair. When cell homogenates were incubated with [3H]-testoterone, the 5α-reductase of beard dermal papila cells exhibited an optimum activity at pH 5.5, whereas the enzyme of dermal papila cells from occipital scalp hair showed a board and low plateau between pH 6.0 and 9.0, without a sharp peak. The apparent Michealis constant of 5α-reductase was 3.3 × 10-7 M in dermal papila cells from beard and 2.4 × 10-5 M in those cells from occiptal scalp hair. The apparent Km of 5α-reductase for NADPH was 2.8 × 10-5 M and 7.6 × 10-4 M in beard and occipital scalp hair dermal papila cells, respectively. There were no significant differences in the substrate specificity between these two types of cells. The 5α-redutase activity recovered mainly in the nuclear fraction of beard dermal papila cells. By, contrast, it was widely distributed among the individual subcellular fractions of dermal papila cells from occipital scalp hair. These results strongly suggest that those of 5α-reductase, and that the enzyme in beard dermal papilla cells is similar in characteristics to that in the androgen target organs such as prostate