Dioxygenase that catalyzes the 2-oxoglutarate-dependent selective hydroxylation of free L-proline to cis-3-hydroxy-L-proline (cis-3-Hyp). D-proline, trans-4-hydroxy-L-proline, cis-4-hydroxy-L-proline, cis-4-hydroxy-D-proline, and 3,4-dehydro-DL-proline are not substrates. 2-oxoglutarate + L-proline + O2 = cis-3-hydroxy-L-proline + CO2 + succinate Binds 1 Fe(2+) ion. Inhibited by metal ions such as Co(2+), Zn(2+), Ni(2+) or Cu(2+). Is also inhibited by EDTA in vitro. Unlike the procollagen-proline cis-3- and trans-4-hydroxylases from mammals, does not necessarily require L-ascorbate for activity although it does increase the activity of the enzyme. Comparison of both proline 3-hydroxylase isozymes shows that type II enzyme has 1.8-fold higher activity than type I upon L-proline, and 24-fold higher activity upon L-2-azetidinecarboxylic acid. Optimum pH is 6.0. Is stable from pH 5.5 to 8.5. Optimum temperature is 35 degrees Celsius. Is stable below 30 degrees Celsius. Homodimer. Belongs to the L-proline cis-4-/cis-3-hydroxylase family.