P4HB（prolyl 4-hydroxylase subunit beta），癌症关联基因，基因ID：5034，该基因编码脯氨酰4-羟化酶的β亚单位，脯氨酰4-羟化酶是一种非常丰富的多功能酶，属于蛋白质二硫化物异构酶家族当以包含两个α和两个β亚单位的四聚体存在时，这种酶参与前胶原中脯氨酰残基的羟基化这种酶也是二硫键异构酶，含有两个硫氧还蛋白域，催化二硫键的形成、断裂和重排。其他已知功能包括其作为伴侣的能力，其以浓度依赖性方式抑制错折叠蛋白的聚集，其结合甲状腺激素的能力，其在S-亚硝基硫醇结合的一氧化氮的流入和流出中的作用，以及其作为微粒体甘油三酯转移蛋白复合物的亚基的功能。[由RefSeq提供，2008年7月]This gene encodes the beta subunit of prolyl 4-hydroxylase， a highly abundant multifunctional enzyme that belongs to the protein disulfide isomerase family. When present as a tetramer consisting of two alpha and two beta subunits， this enzyme is involved in hydroxylation of prolyl residues in preprocollagen. This enzyme is also a disulfide isomerase containing two thioredoxin domains that catalyze the formation， breakage and rearrangement of disulfide bonds. Other known functions include its ability to act as a chaperone that inhibits aggregation of misfolded proteins in a concentration-dependent manner， its ability to bind thyroid。