Placental Amino Acids Transport in Intrauterine Growth Restriction

Table 1

Amino acids transport systems in the human placenta.

Transport system	Protein	Localization	Substrate
Na^+-dependent systems
A	SNAT1, 2, 4	MVM, BM	Neutral amino acids
ASC	ASCT1, 2	BM	Neutral amino acids
𝛽	TAUT	MVM, BM	Taurine
N	SN1	MVM (contested in humans)	Histidine, asparagine, glutamine
X^−AG	EAAT1–4	MVM, BM	Anionic amino acids
GLY	GLYT1	MV	Glycine and sarcosine
B^0,+	ATB^0,+	?	Cationic and neutral amino acids
Na^+-independent systems
L	LAT1, 2, 4/4F2hc	MVM, BV	Neutral amino acids, branched-chain amino acids, and tryptophan
y^+	CAT1, 4	MVM, BV	Cationic amino acids
y^+L	y^+LAT1/4F2hc	MVM, BM	Cationic amino acids (neutral amino acids in the presence of sodium)
b,^0,+	rBAT	BM	Cationic and neutral amino acids
T	TAT1	BM	Aromatic amino acids
asc	asc1/4F2hc	BM?	Small neutral amino acids and D-serine

MVM: microvillous membrane.
BM: basal membrane.
Modified from [15–17].