Biotin
Propionate ± Propionyl CoA =± methylmalonyl CoA (D)
Racemase B12
Methylmalonyl CoA (L) Succinyl CoA Succinate
Delivered at the annual meeting, American Academy of Pediatrics, New York, October 16, 1972. Supported by U.S. Public Health Service grant AS16526-01.
ADDRESS: (LAB.) Department of Pediatrics, College of Medicine, University of South Florida, Tampa,
Florida 33620.
METHYLMALONIC
ACID
1012
Borden
Award
Address
Lewis A. Barness, M.D.
From the Department of Pediatrics, College of Medicine, University of South Florida, Tampa, Florida
T
HE kindness of the Academy inbe-stowing this honor makes me question
the judgment of those who have put me in
the category of the preceding winners.
Af-ter discovering methylmalonic acid in rat
urine, I found that it had been discovered
about 20 years before in rat urine. After
finding it, we misinterpreted its meaning;
and after learning its true meaning, we
missed the first case of methylmalonic
ac-idemia.
Dr. Paul Gyorgy had challenged me to
look for those metabolic differences which
occurred in rats developing liver necrosis.
We felt assured that what is new in rat
liv-ers today will 1e true in children tomorrow.
We studied urine from necrotic rats and
normals. We never did find the differences,
but Ms. Helga Moeksi Suld, Dr. Martin
Forbes, and P found that many of these
rats excreted an organic acid, later
identi-fied as methylmalonate. We further found
that the excretion of methylmalonate
de-creased on the addition of aureomycin and
other antibiotics,2 a finding to be mentioned
later. With Drs. Barnabei, and Valyasevie,3
we found that methylmalonate could be
de-rived from thymine, valine, or propionate.
We thought methylmalonate had
some-thing to do with vitamin E deficiency, but
even now we are not sure it does not. Drs.
Oski and Tedesco have particularly favored
this approach. Then, several real
biochem-ists discovered that methylmalonate was
converted to succinate via a B12-dependent
enzyme.4’5 Drs. Kahn, Williams, Meilman,
Diane Young, and 16,7 showed that the
pres-ence of methylmalonate in biological fluids
was a very sensitive indicator of vitamin B12
deficiency:
Drs. Kaye and Baker then presented us
with a patient with severe acidosis. We
noted he excreted huge quantities of
meth-ylmalonate. We studied his vitamin B,2
and E status for a long time to no avail.
Then Oberholzer reported a patient with an
inborn error of the enzyme methylmalonyl
CoA mutase.8 Dr. Morrow and I then
real-ized that our patient had a similar defect.
Delineation of this defect has led to the
finding by many of a group of diseases
im-portant as inborn errors of metabolism,
some of which are treatable, and also
im-portant as tools in the better understanding
of acidosis.
METHYLMALONIC ACIDEMIA
At least three forms of methylmalonic
ac-idemia are known. These usually develop in
infancy with intractable acidosis, vomiting,
and hyperglycinemia. Some are mentally
retarded. Other major clinical features
in-clude lethargy, hepatomegaly, failure to
grow, ketoacidosis, neutropenia, and
thrombocytopenia. Megaloblastic anemia
was not observed. Vitamin B,2 levels were
normal or elevated in all these children.
In one type of methylmalonic acidemia,
ARTICLES 1013
the vitamin B,2 responsive type,#{176}the
symp-toms may be less severe than those of the
unresponsive type. In the responsive form,
coenzyme biosynthesis is defective.
Coen-zyme administration to cells or massive
doses of the vitamin alleviate the difficulty.
In the unresponsive forms, the apoenzyme
is defective and treatment is symptomatic.1#{176}
A third form of the disease has recently
been described in one newborn infant who
died and was reported to have a racemase
deficiency. In addition to a severe acidosis,
the baby had hyperammonemia.h1
Yet another disease with methylmalonic
acidemia has been described with
homocys-tineniia. This child had seizures, lethargy,
and poor muscle tone, but ketoacidosis was
not a problem early. This patient died at
about 8 weeks of age.12
Methylmalonic acidemia is one of the
few disorders which can be diagnosed
pre-natally by finding abnormal quantities of
the metabolite in both the urine of the
mother during pregnancy and in the
amni-otic fluid.13
The fact that this metabolic pathway is
developed early in fetal life suggests that
the propionate-succinate conversion is
im-portant in the metabolism of the fetus.
OTHER
INFANTILE
ACIDOSES
Propionic Acidemia
Several patients with severe ketoacidosis
and hyperglycinemia have been described.
All children failed to thrive. All required
prolonged base treatment, though some
seemed improved spontaneously. Several of
these patients have responded to biotin
ad-ministration.’ 5-18
Isovaleric Aciderriia
Episodic ketoacidosis and coma,
associ-ated with elevations of isovaleric acid in the
blood have been found due to a deficiency
in isovaleryl-CoA dehydrogenase, resulting
in a block in leucine metabolism. These
pa-tients excreted N-isovalerylglycine.9’2#{176}
Several other forms of persistent acidosis
in infancy have been described. A
6-month-old infant with succinyl-CoA transferase
de-ficiency had intermittent ketoacidosis and
ketonuria.h1 A 5-month-old infant with
biotin responsive 3-methyl
crotonylglyci-nuria had persistent metabolic acidosis and
ketosis.22 He also excreted
hydroxyisoval-eric acid. Improvement occurred after the
administration of biotin, and the abnormal
metabolites disappeared from the urine.
These metabolites are breakdown products
of leucine.
Lactate-Pyruvate Acidosis2328
Several children with mental retardation
and acidosis had increased concentrations
of lactate and pyruvate in the blood and
urine. In some, alpha ketoglutarate or alpha
alanine has also been elevated. This disease
is apparently inherited as an autosomal
re-cessive. The symptoms start in early infancy
with hyperventilation, hypotonia, mental
retardation, and seizures. Frequently, the
acidosis requires continuous base
adminis-tration to prevent symptoms of acidosis.
Death occurs in childhood. It has been
sug-gested that a defect in pyruvic carboxylase,
or other citric acid cycle enzymes, perhaps
related to thiamine metabolism, is
responsi-ble for the condition. This disease is similar
to that described as Leigh’s
encephalomy-elopathy. In a child described by Lonsdale
et al.,23 there was an apparent response to
massive doses of thiamine.
A child with deficient hepatic fructose 1,6
diphosphatase activity and fasting
hypo-glycemia has severe intermittent acidosis.24
Methylmalonic Acid in Vitamin B,2 Deficiency
In searching for methods to determine
vi-tamin status, several approaches have been
used. Early, deficient states and their
cor-rection was the most direct and most
obvi-ous method. As gross vitamin deficiency
states have become less common, blood
lev-els of vitamins and loading tests have been
utilized. Because of great variability of
nor-mal and the frequency of incongruities
be-tween blood levels and biochemical
abnor-malities, a more direct approach of vitamin
is being instituted. Methylmalonate
excre-tion as a sensitive test for vitamin B12
defi-ciency is such an approach. One possible
source of error in methylmalonate excretion
is that it may be normal if antibiotics are
given,2 but otherwise appears to be a very
sensitive test of vitamin B,2 deficiency.29
CONCLUSION
Methylmalonate studies have led to some
understanding of vitamin B,2 metabolism
as well as certain inborn errors of
metabo-lism. These, in turn, have served as models
of a group of diseases related to acidosis, so
that the study of organic aciduria at present
is similar to that of amino aciduria 20 years
ago. Techniques for studying these have
been developed.
Many unanswered questions remain.
( 1) What does methylmalonate do?
Does it, itself, cause the acidosis? Does it
cause a deficiency of succinate in the
oxida-tive cycle?
(
2)
Are more direct ways of increasingsuccinate available?
( 3)
What is the relation ofmethylmalo-nate to combined system disease or vitamin
B,, neuropathy?
(4) Are enzymes defective or absent?
(5) What is the significance of
methyl-malonate in the newborn?
(6) How does one counsel or treat
fami-lies which include members with
methyl-malonic aciduria?
REFERENCES
1. Barness, L. A., Moeksi, H., and Cyorgy, P.: Urinary excretion of methyhnalonic, a,
methyl succinic and other ether-soluble ac-ids in rats. J. Biol. Chem., 221:93, 1956. 2. Forbes, M., Barness, L. A., Moeksi, H., and
Cyorgy, P.: Excretion of ether soluble acids by rats on necrogenic diet with and without supplements of antibiotics. Proc. Soc. Exp. Biol. Med., 84:162, 1953.
3. Barnabei, 0., Valyasevi, A., Barness, L. A.,
and Gyorgy, P.: Sources of methyhnalonate
in rat urine: Valine metabolism. Arch. Bio-chem. Biophys., 69:259, 1957.
4. Flavin, M., and Ochoa, S.: Metabolism of
propionic acid in animal tissue: I. Enzymatic
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5. Stadtman, E. R., Overath, P., Eggerer, H., and
Lynen, F.: The role of biotin and vitamin
B,2 coenzymes in propionate metabolism. Biochem. Biophys. Res. Comm., 2: 1, 1960. 6. Barness, L. A., Young, D., Mellman, W. J.,
Kahn, S. B., and Williams, W. J.: Methylmal-onate excretion in a patient with pernicious anemia. New Eng. J. Med., 268: 144, 1963. 7. Bamess, L. A., Young, D. C., and Nocho, R.:
Methylmalonate excretion in vitamin B12 deli. ciency. Science, 140:76, 1963.
8. Oberhoizer, V. C., Levin, B., Burgess, E. A.,
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me-tabolism. Pediat. Res., 2:519, 1968.
18. Hsia, Y. E., Scully, K.J., and Rosenberg, L. E.:
Defective propionate carboxylation in ketotic
hyperglycinemia. Lancet, 1:757, 1989.
17. Barnes, N. D., Hull, D., Balgobin, L., and
Compertz, D.: Biotin-responsive propionic
acidemia. Lancet, 2:244, 1970.
18. Ando, T., Rasmussen, K., Nyhan, W. L.,
Don-nell, C.,and Barnes, N. D.: Propionic
acide-mia in patients with ketotic hyperglycine-mia. J. Pediat., 78:827, 1971.
19. Tanaka, K., Orr, J. C., and Isselbacher, K. J.: Identification of -hydroxyisovaleric acid in the urine of a patient with isovaleric
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20. Eldjarn, L., hum, E., Stokke, 0., Paude, H.,
acidu-ARTICLES 1015
phy. na and B-methylcrotonylglycinuria: A new inborn error of metabolism. Lancet, 2:521,
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21. Cornblath, M., Gingell, R. L., Flemong, C. A., Tildon, J. T., Leffler, A. T., and Wapnir, R. A.: A new syndrome of ketoacidosis in in-fancy. J. Pediat., 79:413, 1971.
22. Gompertz, D., Draffan, C. H., Watts, J. L., and Hull, D.: Biotin-responsive B-methyl-crotonylglycinuria. Lancet, 2:22, 1971. 23. Lonsdale, D., Faulkner, W. R., Price, J. W.,
and Smeby, R. R.: Intermittent cerebellar ataxia associated with hyperpyruvic ac-idemia, hyperalaninemia and hyperalanin-uria. PEDIATRICS, 43:1025, 1969.
24. Baker, L., and Winegrad, A. I.: Fasting hypo-glycemia and metabolic acidosis associated with deficiency of hepatic fructose 1-6
di-phosphatase activity. Lancet, 2:13, 1970.
25. Podos, S. M.: Hyperpyruvicemia with hyper-alpha-alaninemia. Arch. Ophthal., 83:504,
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28. Haworth, J. C., Ford, J. D., and Younoskai,
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Acknowledgment
Obviously, I did not do most of this work. I should like to thank my technicians Ms. Moeksi, Young, Bockris, Maresca, and Mr. R. Nocho, and
especially my colleagues, Drs. P. Cyorgy, F. Oski, W. Mellman, C. Morrow; to my secretary of many
years, Ms. Verdie Honan Thomas, and the many
