About Beans by Stanley Scharf....


On July 10, 2012   I read an article : "Nutrition Notes: Beans are a
healthy source of protein"  by a Syracuse based dietician,  in the
Syracuse Post Standard, which I knew  immediately contained  some
misconceptions on 'vegetable protein'. The offending sentences  were :
"A complete protein contains all the essential amino acids (your body
can manufacture the rest from these). Soybeans are the only bean with
"complete" protein, like animal sources".

My response ---after  some  research--- was to write the article attached below.
Needless to say, I was completely blown away by what
had been learned over the past 30 years; absolutely stunned.

When it comes to seed storage proteins, Nature is conservative!

All spermatophytes  (seed bearing plants) except for the grass family
contain soybean-like 7S & 11S seed storage proteins. The cereals, oats
and rice, also contain a
majority of soybean protein.

The living spermatophytes form five groups:
The first four belong to Gymnosperms;  plus  Angiosperms.

*  Cycads, a subtropical and tropical group of plants with a large
crown of compound leaves and a stout trunk,

 * Ginkgo, a single living species of tree,

* Conifers, cone-bearing trees and shrubs,

 * Gnetophytes, woody plants in the genera Gnetum, Welwitschia, and Ephedra, and

*Angiosperms, the flowering plants, a large group including many
familiar plants in a wide variety of habitats. (Monocots & Dicots)

***The story of 7S & 11S is nothing....less than the evolution of
plant life on planet Earth................

Seeds are the largest reserve of protein on the planet after animals.
They  are the major reproductive  and dispersal  organ of plants. Seed
crops : grain, pulses, and  oilseeds, for food,  surpass total world
yields of  tuber crops many fold.  Protein, starch and lipids  are the
rich storage reserves  exploited by humankind  that the seed  produces
to nourish the developing embryo and early stages of seedling growth.

Mature seed storage proteins   that pass 'quality control  monitors'
as being  correctly formed  and assembled are stably accumulated in
'protein bodies' within the seed. During germination and seedling
growth the storage proteins are cleaved by proteolytic enzymes into
small peptides or amino acids that are subsequently transported to the
growing seedling.  Proteolysis (digestion) occurs only after a  long
period of rest and imbibition of water, when seeds germinate and
seedlings start to grow . Synthesis and proteolysis, the antagonistic
processes of protein turnover, occur during different developmental
stages and
represents  a dilemma in storage protein metabolism.

The  immense value of seed crops  is facilitated by their   being
harvested in a dry state with good storage properties, yet  remaining
viable and easily rehydrated. This inherent desiccation/hydration
property of seeds  represents an evolutionary pathway taken by  a
group of  ancient  proteins  involved
in basic cellular processes associated with  desiccation and
hydration. An extant ,common, fern , Matteuccia struthiopteris, the Ostrich
fern, (its  fiddlehead  stage is eaten as a spring  cooked vegetable)
is very likely the common ancestor of both a  spore-specific ,
vicilin-like protein( a  fern gene is specifically  expressed) and
spore-specific,  legumin-like protein and spermatophytes, (seed
plants) containing storage proteins defined by their svedberg (S)
sedimentation coefficients 7S for vicilin and 11S for legumin.

The fern protein can be considered as a -- molecular missing link-- between a
single domain (one gene)  for    germins and germin-like proteins (GLP's, from
the word  germinating) which constitute a large and highly diverse
family of ubiquitous plant proteins, in  prokaryotes (bacteria, etc)
and  two domain (multigene) seed storage globulins  of
gymnosperms(conifers) and angiosperms(flowering plants). Seed storage
globulins of spermatophytes evolved  from desiccation-related
single-domain  proteins of prokaryotes via a duplicated two-domain
ancestor that is best represented by the extant fern spore-specific 7S
vicilin-like protein.

The 'cupins' are a large and functionally immensely diverse
superfamily of proteins that have a common origin and whose evolution
can be followed from bacteria to eukaryotes including animals and
higher plants . These proteins share a common architecture described
as a six-stranded  β-barrel structural core domain to which the term
cupin (derived from the Latin word cupa for  small barrel)  but also
"jelly roll" β-barrel has been used. Cupins can be divided into
single-domain cupins and two-domain bicupins. Monocupins include
bacterial (enzymes) carbohydrate isomerases and epimerases, metal-dependent
dioxygenases as well as germins and germin-like proteins. The largest
families of bicupins are the 7S and 11S seed storage globulins that
are the major components of plant seeds and constitute important
protein sources of the human diet.

The 7S globulin is a duplication of a primordial gene;  and  the 11S
globulin  is a triplication of the  same primordial gene. This ancient
gene  is represented by either the amino-terminal domain or the
carboxyl-terminal domain of the subunit protein. In either case
the opposite half of the protein( head of protein is carboxyl and tail
is amino) represents the  gene expression  from the duplicated  gene
in 7S.

In legumes ( soybeans, peas, beans, etc)  "seed storage protein" and most globulins are insoluble in water at their isoelectric point, but
are solublized in the presence of salt. The addition of NaCl to 0.7N
will make most of the soy proteins, for example. soluble at their
isoelectric point which is pH  4.2.
"Seed globulin"  are used interchangeably  where most of the  storage
protein  is by Osborne's( Thomas Burr) classical  definitions,
globulin, i.e., soluble in dilute salt solution but insoluble in

The combination  of 7S vicilin  and its  closely related offspring the
11S legumin,  is the storage protein synonymous with soybean (soy)
protein  {the Gold standard of vegetable protein }. The protein
content of soybeans , at  about 40%, far exceeds that of other legumes
except for lupine(Lupinus species) where the Andean species, Lupinus
mutabilis,  called  locally 'chocho' can reach up to 50%  along with
20% oil content.  Soybean-type ( 7S and/or 11S) globulin seed storage
proteins  are, however,  not at all confined  to legumes but are
spread  among almost all plants.  Most  angiosperms , both
dicotyledonous (dicot) , as well as  monocotyledonous( monocot) plants
(with one big exception, see below) synthesize, process and deposit
soybean-type (7S and/or 11S) globulins  as  storage proteins. The
seeds of  both angiosperms and gymnosperms {for example Metasequoia,
ginkgo, sunflower,  Douglas fir, pines, English oak, cocoa,
coffee(coffee grinds), Cruciferous vegetables, Brazil nut,  beans,
peas, buckwheat, quinoa , pumpkin, oats and rice } contain
soybean-type globulins in varying amounts to provide nitrogen and
sulfur as well as carbon skeletons.

The  sulfur amino acid dense  2S albumin  storage proteins form a
major  group of storage
proteins in many dicotyledonous plant species including legumes. The
kernel embryo of the  monocot , oil palm , consists of  some 2S
albumin but mostly 7S  soybean-type  globulin whereas  Cocosin  the 11
S globulin of coconut endosperm is  identical to  soybean


For the 11S protein, soy  glycinin for example, to fold properly
helped by chaperone ( heat shock proteins) into its hexagonal
shape(containing six subunits, a hexamer), it must
undergo a very limited proteolysis in a manner similar to the
cleavageof a peptide from proinsulin to obtain active insulin. A newly
discovered (1991) novel  proteinase  in plants called 'legumain'
(family C13) can now  also be added to the list of   three (3)  known
mammalian cysteine endopeptidases, namely,  Papain  which constitutes
the C1 family of protease clan CA in the MEROPS database
{http://merops.sanger.ac.uk/cgi-bin/family_index?type=P#C} which
include  cathepsins B,H,L,S and others; Calpain (family C2 ); and
Caspase(family C14).

Legumains ( asparaginyl proteinases), also called VPE, vacuolar
processing enzyme, are a family of plant and animal (Asn) asparagine -
specific cysteine proteinases with extra-cytoplasmic localization in
vacuoles or cell walls. Very recently ,February, 2012 ,  3-D modeling
has underlined the similarity  of its active site
with caspases which are (Asp) aspartic - specific proteinases involved
in cell apoptosis. Caspases are essential in cells for apoptosis, or
programmed cell
death, in development and most other stages of adult life, and have
been termed "executioner" proteins for their roles in the cell.
Failure of apoptosis is one of the main contributions to tumor
development and autoimmune diseases; moreover unwanted apoptosis
occurs with ischemia or Alzheimer's disease.

After  a prolonged  seed dormancy and imbibition of water   legumains
very  similar to VPEs  which are synthesized in abundance during
germination and seedling growth contribute  greatly to the  subsequent
 'unlimited' degradation of storage  globulins to amino acids.  Legmains degrade
storage globulins in combination with papain-like enzymes and
carboxypeptidases also present in protein bodies.

The  one big exception to the rule of  soybean-type globulins    are the
monocot  temperate cereals, wheat, rye, barley, related
wild grasses and the  tropical cereals, maize(corn), sorghum, millet
and Coix(Job's tears) where prolamins (high in the amino acid proline
and glutamine) are the major storage proteins aside from oats and
rice(in which they are minor components).  While prolamin based
cereals are significantly inferior in quality to soybean-type globulin
protein they none-the-less provide some 75% of  human food.

Prolamins which are so characteristic of  cereals and are universally
present in  the seeds  of  all other species of the Gramineae (grass)
have not so far been detected in any other  plant families. Almost
unique to wheat  is gluten comprised of the prolamines gliadins and
glutenins. Bread wheat is a hexaploid and wheat for pasta is a

Grasses are relative new comers to the Earth's  flora  and their rise
to dominance is one of the most dramatic events of biome evolution in
Earth history. Grasses possess two main photosynthetic pathways: the
C3 pathway,  that is typical of most plants and a specialized C4
pathway, { C4 plants  most likely evolved under concentrations of
atmospheric  CO2 lower than current CO2  levels; 394.29 ppm as of July
2012}  which acts as a  CO2  pump,  concentrating CO2 for its initial
fixation  , minimizing   respiration during photosynthesis
and thus increasing water conservation  and photosynthetic efficiency
in high radiation, high-temperature, and/or low-CO2 environments. C4
grasses dominate tropical and subtropical grasslands and savannas, and
C3 grasses dominate the world's cooler temperate grassland regions.

Some warm-season  annual crops of economic importance using the C4
photosynthetic pathway  are maize(corn), , sorghum, Sudan grass, pearl
millet. Perennial warm-season crops include sugarcane;  big
bluestem and Indian grass, iconic grasses of the  'Tall Grass Prairie'
as well the the much touted biomass / biofuel native crop switchgrass.

The Frosting on the Cake is the fact that.........
Essential cocoa/chocolate-specific aroma
precursors---aroma-relevant-peptides-- are generated during
fermentation of cocoa seeds by proteolysis  of the soybean-type, cocoa 7S
vicilin globulin.  The proteolytic formation of the cocoa-specific
aroma precursors was investigated in vitro using protein substrates
and proteases purified from ungerminated cocoa seeds. An aspartic
endoprotease( splits protein into large peptide fragments) and a
carboxypeptidase (removes terminal amino acids one-at-a-time)present
in ungerminated cocoa seeds were found to be required for this
process. Cocoa/chocolate-specific aroma precursors were obtained by
proteolytic digestion of the  soybean-type vicilin globulin but not by
proteolysis of the albumin of cocoa seeds.





The primary reference:  Seed Proteins; Peter R. Shewery and Rod Casey(Eds) 1999.
Kluwer Academic Publishers,Dordrecht,The Netherlands
The  883 page volume is  dedicated to Thomas Burr Osborne  who was one
of the founding fathers of protein chemistry; and along with his very
close colleague Lafayette Mendel of Yale,  co-founded the science of
nutrition. http://en.wikipedia.org/wiki/Lafayette_Mendel

Osborne spent the years 1886 till 1928 working at the Connecticut
Agricultural Experiment Station in New Haven.. where he wrote 'The
Vegetable Proteins' published in 1924.

Also take a look at this:(ya gotta love it)