. 2014 Nov 5;88(12):2135–2190. doi: 10.1007/s00204-014-1382-8

Table 11.

Representative non-CYP-xenobiotic-metabolizing enzyme activities^a in human skin and human cells in culture

Substrate (preferentially for)	Skin	Keratinocytes^b	HaCaT	NCTC 2544	KeratinoSens^®	LuSens	U937	THP-1
Benzydamine (broad-spectrum FMO substrate)	+				bd	bd	bd	bd
Arachidonic acid (COX)	23.5 ± 8.7^c	5.1 ± 2.8^c	0.05 ± 0.03^c	0.02 ± 0.01^c
Ethanol (ADH)	0.3–0.4^d				bd	bq	bd	bq
Propanal (ALDH)				8 ± 1.5^m	4.77–16.4^d	8.04–17.3^d	bd	bq
2,6-Dichlorophenol indophenol (NQR)	~350^d	~340^d,e ~880/1320^d,f		134 ± 0.05^d
Menadione (NQR)	7–10^d/~ 11^d,g	~88^d	~288^d
Fluorescein diacetate (E)	~0.5^h	3.7^h			3.20–4.06^h	1.19–3.55^h	0.911–1.057^h	0.869–1.072^h
4-MU heptanoate (E)	10–32^j	23^j
CDNB (GST)	~290^f,j	~620^d; ~50^j	~47^j	~40^m 167 ± 3^m/234^m
Para-nitrophenol (UGT)		0.016–0.023^j
4-MU (UGT)	1.3 ± 0.2^k	bd to ~1.2^j	1.99 ± 0.97^j	~1^j	bd	bd	bd	bd
PABA (NAT)	0.449 ± 0.175^h	0.215 ± 0.070^h 8 ± 0.5^l	12.0–44.5^l		13.3–28.7^h	10.9–22.6^h	24.8–60.2^h	6.00–29.9^h
Para-toluidine (NAT)	0.63–3.03^d	0.16 ± 0.08^j	0.65 ± 0.37^j	0.35 ± 0.22^j

More examples and references in the text

4-MU 4-methylumbelliferone, ADH alcohol dehydrogenase, ALDH aldehyde dehydrogenase, DCNB 1-chloro-2,4-dinitrobenzene; E esterase, FMO flavin-dependent monooxygenase, bd below the limit of detection, bq below the limit of quantification, NQR NADH/NADPH quinone reductase, PABA para-aminobenzoic acid

^aConstitutive; number after slash: induced (highest reported induced activity)

^bKeratinocytes = Primary keratinocytes in culture (“NHEC,” “normal human epithelial keratinocytes”)

^cpg prostaglandin E2 formed/min/mg microsomal protein

^dnmol/min/mg cytosolic protein

^eDifferentiated keratinocytes

^fProliferating keratinocytes

^gEx vivo epidermis

^hnmol/min/mg S9 protein

ⁱEpidermis (scraped from skin surgical samples)

^jnmol/min/mg protein, activity determined in culture medium

^knmol/min/mg microsomal protein

^lnmol/min/mg cell lysate protein

^mnmol/min/mg homogenate protein