unreviewed

(LDLR-mediated endocytosis; lysosomal acid lipase; PCSK9 regulation)

1 reactions · 1 pathways

What it does, reaction by reaction

1 reactions

Lipoprotein Metabolism (Exogenous and Endogenous Pathways: chylomicrons, VLDL, LDL, HDL) Lipid Metabolism · Intestine, liver, plasma, capillary endothelium

step 12 Irreversible/directional

LDL + LDLR → endocytosed LDL; cholesteryl ester → free cholesterol

Converts LDL LDLR into Endocytosed LDL Cholesteryl ester

› Notes

ApoB-100 binds LDLR, triggering clathrin-mediated endocytosis. Endosomal acidification releases LDL from receptor; LDLR normally recycles, while lysosomal acid lipase releases free cholesterol. PCSK9 directs LDLR toward lysosomal degradation rather than recycling and thereby raises circulating LDL.

Showing all 1 reactions.

What accelerates and inhibits it

Regulation is pathway-specific, so each context is listed separately

0 entries

No regulation recorded for this enzyme in the source documents.

Disorders

Abetalipoproteinaemia
MTTP AR

Fat malabsorption, acanthocytosis, retinitis pigmentosa, ataxia, fat-soluble vitamin deficiency
Acute intermittent porphyria
HMBS AD

Abdominal pain, neuropathy, psychiatric signs, port-wine urine; NO photosensitivity; triggered by CYP inducers, fasting, alcohol
Adenosine deaminase deficiency
ADA AR

Severe combined immunodeficiency; absent T, B and NK cells
Alkaptonuria
HGD AR

Urine darkens on standing, ochronosis of cartilage, degenerative arthritis
Andersen disease (GSD IV)
GBE1 AR

Cirrhosis, failure to thrive, early death
Argininosuccinic aciduria
ASL AR

Hyperammonaemia, trichorrhexis nodosa (brittle hair)
Citrullinaemia type I
ASS1 AR

Hyperammonaemia, vomiting, encephalopathy
Classic galactosaemia
GALT AR

Cataracts, jaundice, hepatomegaly, intellectual disability, E. coli sepsis
Cori-Forbes disease (GSD III)
AGL AR

Milder than GSD I; normal lactate, hepatomegaly, myopathy
CPS I deficiency
CPS1 AR

Neonatal hyperammonaemia, lethargy, coma
CPT-I deficiency
CPT1A AR

Hypoketotic hypoglycaemia, hepatomegaly; normal or high carnitine
CPT-II deficiency
CPT2 AR

Adult form: rhabdomyolysis after prolonged exercise or fasting
Crigler-Najjar syndrome type I
UGT1A1 AR

Severe neonatal jaundice, kernicterus, death without transplant
Cyanide / carbon monoxide poisoning
(acquired) Acquired

Headache, coma, lactic acidosis; cherry-red skin in CO; bitter-almond odour in cyanide
Cystinuria
SLC3A1 / SLC7A9 AR

Recurrent hexagonal cystine kidney stones
Diabetic ketoacidosis
(acquired) Acquired

Hyperglycaemia, high anion-gap acidosis, Kussmaul breathing, acetone breath, dehydration
Dubin-Johnson syndrome
ABCC2 AR

Conjugated hyperbilirubinaemia; grossly black liver
Essential fructosuria
KHK AR

Benign; asymptomatic
Essential pentosuria
DCXR AR

Benign; incidental urinary reducing substance
Fabry disease
GLA XR

Angiokeratomas, acroparaesthesia, hypohidrosis, renal failure, cardiomyopathy, stroke
Familial chylomicronaemia (type I)
LPL / APOC2 AR

Eruptive xanthomas, lipaemia retinalis, recurrent pancreatitis; creamy supernatant
Familial hypercholesterolaemia
LDLR / APOB / PCSK9 AD

Tendon xanthomas, xanthelasma, corneal arcus, premature coronary disease
Fructose-1,6-bisphosphatase deficiency
FBP1 AR

Fasting hypoglycaemia with lactic acidosis and ketosis, hyperventilation
G6PD deficiency
G6PD XR

Episodic haemolysis with oxidants (primaquine, sulfonamides, nitrofurantoin, dapsone, fava beans, infection); Heinz bodies, bite cells
Galactokinase deficiency
GALK1 AR

Isolated cataracts, no hepatic or CNS disease
Gaucher disease
GBA AR

Hepatosplenomegaly, pancytopenia, bone crises, Gaucher (crumpled-tissue-paper) cells
Gilbert syndrome
UGT1A1 AR / polymorphism

Mild intermittent jaundice with fasting, illness or stress; otherwise benign
Gout
(multifactorial) Multifactorial

Acute podagra; negatively birefringent needle-shaped crystals; tophi
Hereditary fructose intolerance
ALDOB AR

Vomiting, hypoglycaemia, jaundice, cirrhosis after fructose/sucrose; aversion to sweets
Hereditary orotic aciduria
UMPS AR

Megaloblastic anaemia NOT responsive to B12 or folate, failure to thrive; NO hyperammonaemia (unlike OTC deficiency)
Homocystinuria (CBS deficiency)
CBS AR

Marfanoid habitus, DOWNWARD lens dislocation, thrombosis, intellectual disability, osteoporosis
Krabbe disease
GALC AR

Optic atrophy, peripheral neuropathy, globoid cells, developmental regression
Lead poisoning
(acquired) Acquired

Microcytic anaemia with basophilic stippling, abdominal colic, wrist/foot drop, encephalopathy, gingival lead lines
Leigh syndrome
mtDNA or nuclear Mitochondrial / AR

Subacute necrotising encephalomyelopathy; brainstem and basal ganglia lesions
Lesch-Nyhan syndrome
HPRT1 XR

Hyperuricaemia, gout, orange sand in nappies, self-mutilation, choreoathetosis, intellectual disability
Maple syrup urine disease
BCKDHA/B, DBT AR

Burnt-sugar/maple urine odour, poor feeding, ketoacidosis, encephalopathy
MCAD deficiency
ACADM AR

Hypoketotic hypoglycaemia on fasting, vomiting, coma, SIDS-like death
McArdle disease (GSD V)
PYGM AR

Exercise intolerance, cramps, myoglobinuria, second-wind phenomenon; normal blood glucose
MELAS
MT-TL1 Mitochondrial

Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes; ragged red fibres
Metachromatic leukodystrophy
ARSA AR

Central and peripheral demyelination, ataxia, dementia
Methylmalonic acidaemia
MMUT / MMAA / MMAB AR

Ketoacidosis, hyperammonaemia, failure to thrive
Niemann-Pick disease A/B
SMPD1 AR

Hepatosplenomegaly, cherry-red macula, neurodegeneration (type A), foam cells
Oculocutaneous albinism
TYR AR

Hypopigmentation of skin/hair/eyes, photophobia, nystagmus, high skin cancer risk
OTC deficiency
OTC XLD

Commonest urea cycle defect; hyperammonaemia, vomiting, encephalopathy; low BUN, no megaloblastic anaemia
Phenylketonuria
PAH / PTS / QDPR AR

Intellectual disability, musty odour, hypopigmentation, eczema, seizures
Pompe disease (GSD II)
GAA AR

Cardiomegaly, hypotonia, early death in infantile form
Porphyria cutanea tarda
UROD AD / acquired

Commonest porphyria; blistering photosensitivity, hypertrichosis, tea-coloured urine; linked to HCV, alcohol, iron, oestrogen
Primary carnitine deficiency
SLC22A5 AR

Cardiomyopathy, hypotonia, hypoketotic hypoglycaemia
Propionic acidaemia
PCCA / PCCB AR

Ketoacidosis, hyperammonaemia, vomiting, hypotonia
Pyruvate carboxylase deficiency
PC AR

Lactic acidosis, hypoglycaemia, neurological disease
Pyruvate dehydrogenase complex deficiency
PDHA1 XLD

Congenital lactic acidosis, neurological impairment; worsened by high-carbohydrate diet
Pyruvate kinase deficiency
PKLR AR

Chronic non-spherocytic haemolytic anaemia; right-shifted O2 curve
Tangier disease
ABCA1 AR

Near-absent HDL, orange tonsils, hepatosplenomegaly, neuropathy
Tarui disease (GSD VII)
PFKM AR

Exercise intolerance with haemolysis; no second wind
Tay-Sachs disease
HEXA AR

Cherry-red macula, hyperacusis/startle, progressive neurodegeneration; NO hepatosplenomegaly
Tyrosinaemia type I
FAH AR

Liver failure, renal Fanconi syndrome, hepatocellular carcinoma, cabbage-like odour
Von Gierke disease (GSD I)
G6PC / SLC37A4 AR

Severe fasting hypoglycaemia, lactic acidosis, hyperuricaemia, hyperlipidaemia, doll-like facies, hepatomegaly
Wernicke-Korsakoff syndrome
(acquired B1 deficiency) Acquired

Confusion, ophthalmoplegia, ataxia; then confabulation and amnesia
X-linked adrenoleukodystrophy
ABCD1 XR

Adrenal insufficiency with progressive demyelination and behavioural change
X-linked sideroblastic anaemia
ALAS2 XR

Microcytic anaemia with ringed sideroblasts and iron overload
Zellweger syndrome
PEX genes AR

Hypotonia, seizures, craniofacial dysmorphism, hepatomegaly, early death

Provenance. Source: Step catalogue. EC numbers, gene symbols and disease links were written from standard biochemistry rather than the uploaded documents, and stay unreviewed until checked against Expasy ENZYME, BRENDA or OMIM.

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