Table 1 Functional roles of human cytochrome P450 enzymes across different families.

1

Two subfamilies: A and B: CYP1A1, CYP1A2, CYP1B1

CYP1A1 is a major extrahepatic cytochrome P450 enzyme that converts a variety of substances to carcinogenic derivatives; CYP1A2 has monooxygenase and cyclooxygenase activities; and CYP1B1 metabolizes polycyclic aromatic hydrocarbons to carcinogenic compounds

[103, 104]

2

Eleven subfamilies: A, B, C, D, E, F, J, R, S, U, W: CYP2A6, CYP2A7, CYP2A13, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP2F1, CYP2J2, CYP2R1, CYP2S1, CYP2U1, CYP2W1

Total number of genes in the CYP2 family is 36 with 16 expressing active enzymes and the rest encoding pseudogenes. CYP2A6 and CYP2B6 are involved in the metabolism of nicotine and some drugs; CYP2C8 has the function of oxygenase; CYP2C9 is the main drug and xenobiotic metabolic enzyme in the liver; CYP2C19 can metabolize a variety of therapeutic drugs; CYP2D6 is responsible for the metabolism of 20–25% of commonly used prescription drugs; CYP2J2 is a major enzyme responsible for the conversion of polyunsaturated fatty acids into bioactive signaling lipids; CYP2R1 converts vitamin D3 in the liver to 25-hydroxyvitamin D3, which is then released into the bloodstream; CYP2U1 is a hydroxylase; CYP2R1 may be involved in arachidonic acid metabolism and vitamin D activation; CYP2E1 metabolizes exogenous toxins such as ethanol; the function of other CYP2s enzymes is not clear, CYP2 family and CYP3A4 (metabolize more than 50% of drugs) synergistic effect.

[105]

3

CYP3A4, CYP3A5, CYP3A7, CYP3A43

CYP3A4 is a glucocorticoid-induced enzyme; CYP3A5 and CYP3A4 are responsible for 50% of drug metabolism mediated by cytochrome P450 enzymes. CYP3A7 can hydroxylate testosterone and 3-dehydroepiandrosterone sulfate; CYP3A43 showed a low level of testosterone 6β-hydroxylase activity

[106,107,108,109]

4

Six subfamilies: A, B, F, V, X, Z: CYP4A11, CYP4A22, CYP4B1, CYP4F2, CYP4F3, CYP4F8, CYP4F11, CYP4F12, CYP4F22, CYP4V2, CYP4X1, CYP4Z1

There are 38 genes in the CYP4 family, of which 11 express active enzymes and the rest encode pseudogenes. CYP4A11, CYP4F2, CYP4F3, CYP4F8, CYP4F11, CYP4F12 and CYP4F22 ω-hydroxylate various lipid molecules; CYP4V2, CYP4X1, CYP4Z1 and other members have shown catalytic activity in some studies, but the specific functions still need to be further confirmed.

[110]

5

CYP5A1

CYP5A1 catalyzes the conversion of prostaglandin H2 to thromboxane A2 (TXA2)

[111]

7

CYP7A1, CYP7B1

Involved in bile acid synthesis

[112]

8

CYP8A1, CYP8B1

CYP8A1 catalyzes the conversion of prostaglandin H2 to prostacyclin; CYP8B1 is involved in bile acid synthesis

[113, 114]

11

Two subfamilies: A and B: CYP11A1, CYP11B1, CYP11B2

CYP11A1, CYP11B1 and CYP11B2 are mitochondrial enzymes that catalyze the synthesis and transformation of steroid hormones

[115]

17

CYP17A1

It has two different activities and participates in the synthesis of steroid hormones

[116]

19

CYP19A1

Involved in steroid hormone synthesis

[117]

20

CYP20A1

May have neurophysiologic effects

[118]

21

CYP21A2

Converts progesterone to 11-deoxycorticosterone and the conversion of 17-hydroxyprogesterone to 11-deoxycortisol

[117]

24

CYP24A1

A mitochondrial enzyme responsible for the degradation of 1,25-dihydroxyvitamin D3

[119]

26

Three subfamilies: A, B, and C: CYP26A1, CYP26B1, CYP26C1

Regulation of retinoic acid homeostasis

[120]

27

Three subfamilies: A, B, and C: CYP27A1, CYP27B1, CYP27C1

CYP27A1 is involved in the conversion of cholesterol into bile acids through a secondary (acidic) pathway; CYP27B1 converts 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3

[121]

39

CYP39A1

Preferred substrate is 24-hydroxycholesterol which is a major product of CYP46A1

[122]

46

CYP46A1

Expressed primarily in neurons of the central nervous system where it plays an important role in metabolism of cholesterol in the brain; 24S-hydroxycholesterol is a potent activator of LXR

[123]

51

CYP51A1

Catalyzes the removal of the 14α-methyl group from lanosterol in the cholesterol biosynthesis pathway

[68]